Introduction

Incidents in virtual environments can begin with a software vulnerability, human error, a configuration weakness, or several of these factors at once. The investigation is rarely limited to the workload. Hypervisors, container runtimes, management consoles, monitoring platforms, identity systems, virtual networks, datastores, backups, and automation accounts all influence what an attacker can reach.

Kaspersky GERT recently investigated two more ransomware cases on ESXi and Proxmox environments in which weak access controls, insufficient network separation, exposed administrative services, and poor management of privileged credentials contributed to the impact. A monitoring system that could reach the virtualization layer also exposed a reusable root credential. Once the attacker controlled that route, ordinary administrative access was enough to affect several hosts. No VM escape was required.

The incidents show why patching and secure configuration must be managed together. A fully patched hypervisor can still be compromised through a shared password, an overprivileged monitoring account, an open SSH path, or an administrator interface reachable from a general server network. NIST guidance places secure configuration baselines, restricted administrative access, current patches, and monitoring across all layers within the same set of sound security practices.

In this article, we’re going to describe both incidents with additional focus on common unsafe practices that were exploited, leading to compromise, as well as remediation tactics. We’ll also discuss the broader scope of threats targeting virtual environments for a better understanding of possible protection strategies.

The connected system defenders must protect

A business virtual environment is not just Hyper-V, VMware, or Docker but rather a connected stack. Management consoles, orchestration tools, monitoring platforms, and automation accounts sit above hypervisors and container engines. Registries, image stores, virtual switches, datastores, and backup systems connect the layers. Applications and business services run at the bottom, while much of the administrative power sits near the top.

The important boundaries extend beyond guest to host. They include workload to management plane, monitoring system to hypervisor, registry to deployment, administrator workstation to console, management plane to storage, and one virtual network segment to another. An attacker only needs one usable route. The possibility of compromise may lie in one stolen or insecurely placed administrator credential rather than in a complex escape exploit. In the GERT case, the compromise route passed through the monitoring platform and included a valid virtualization platform credential.

Case #1: From network monitoring to ESXi encryption

The investigation began with evidence of BlackNevas ransomware activity on a Windows system in a virtualized domain controller segment. UserAssist artifacts recorded execution of the AnyDesk RMM tool and GMER binaries. The environment also used PRTG Network Monitor to monitor its virtual infrastructure.

UserAssist artifacts

The available evidence showed that the PRTG deployment had broad access to the ESXi hosts and that the same root password was reused across several nodes. After obtaining access to the monitoring environment, the attacker used the ESXi credential to connect over SSH to the hosts that shared the same password. This design joined monitoring, credential storage, and direct administration into one attack path.

PRTG supports storing VMware credentials at the device or inherited group level. That feature is operationally useful, but a monitoring server becomes privileged infrastructure when it holds credentials that can administer the systems it observes. The security question is therefore not whether monitoring needs access, but whether the identity, privileges, storage method, and permitted network path are limited to the monitoring task.

The threat actor gained root access to the ESXi environment and used the esxcli command to bypass the system restriction by disabling the execInstalledOnly policy to execute the encryption binary and also perform anti-forensic log deletion. Let’s look closely at the timeline of the initial host compromise.

ESXi (192.168.*.*) timeline

2025-10-18 Connection attempts from IP address 192.168.*.*.
2025-10-19 During an SSH session by root from IP 192.168.*.*, the file esx is uploaded to the system.
2025-10-19 User "root" attempts to execute the binary esx with the error "Execution of non-installed file prevented".
	chmod 777 esx
	./esx /log
2025-10-19 User "root" deactivates the execInstalledOnly option.
	esxcli system settings advanced set -o 
	/User/execInstalledOnly -i 0
2025-10-19 User "root" executes the malware esx.
2025-10-19 New connection attempts from IP 192.168.*.*.

Now, at the same time, the following activities ensued on a different host with the same password for the root user:

ESXi (172.16.*.*) timeline

2025-10-19 SSH connection by user "root" from IP 172.16.*.*.
2025-10-19 User "root" executes the malware esx and clears the logs.
	chmod a+x esx && chmod 777 esx
	./esx /selftest
	nohup ./esx /p /vmfs/ /depth 5 /log /wipe
	./esx /depth 5 /log /wipe

Case #2: Credential notes impacting the whole Proxmox environment

GERT responded to a ransomware incident by The Gentlemen group, in which the threat actor gained access to Proxmox using information collected during the dwell time between initial access and visible impact. On a compromised system administrator workstation, the actor discovered administrative credentials and access details stored in notes in plain text. These records provided the information needed to log in to Proxmox using the root account.

The actor then activated the VNC web socket through the compromised root account, gaining extensive control over the Proxmox environment. This access was subsequently used to download and execute ransomware within the cluster, which resulted in the encryption of the entire virtual environment. Below are the log records showing the root account being used to access other hosts via a VNC web socket.

root@pam [01/08/2026:00:28:36 -0400] "GET /api2/json/nodes/******/vncwebsocket?port=5900&vncticket=****
root@pam [01/08/2026:00:30:17 -0400] "GET /api2/json/nodes/******/vncwebsocket?port=5900&vncticket=****
root@pam [01/08/2026:00:31:19 -0400] "GET /api2/json/nodes/******/vncwebsocket?port=5900&vncticket=****
root@pam [01/08/2026:00:43:38 -0400] "GET /api2/json/nodes/******/vncwebsocket?port=5900&vncticket=****
root@pam [01/08/2026:00:44:49 -0400] "GET /api2/json/nodes/******/vncwebsocket?port=5900&vncticket=****

This incident is a clear example of the risks of storing privileged credentials in unsecured notes or other easily accessible files. Once the administrator workstation was compromised, the saved credentials allowed the actor to move from a single endpoint into the virtualization management layer. Because the credentials belonged to a highly privileged root account, one poor credential handling practice significantly increased the scope and impact of the attack. Privileged credentials should instead be stored in an approved password manager or privileged access management system, protected with multifactor authentication and rotated immediately if an administrator workstation is suspected of being compromised.

Why the misconfiguration caused broad impact

Both cases exhibited unsafe misconfiguration practices whose exploitation led to a bigger impact on the host system. Next, we will break down each misconfiguration to see how it enabled further compromise and what should be done to avoid it.

Monitoring inherited excessive privilege

In Case 1, the monitoring platform could do more than collect health and performance data. It held or could use credentials with enough privilege to reach ESXi directly. A compromise of the monitoring system therefore became a compromise of the management plane. Monitoring identities should be dedicated to the task and given only the permissions required by the deployed sensors.

Credential reuse

Password reuse converted one recovered secret into farm-wide access. System administration should use named identities through the central management plane. Each host should have unique credentials and proper password storage hygiene. Password strength alone does not limit the impact of theft, but where the credential can be used and where it is stored do.

Direct root access bypassed central control

Direct SSH access allowed the actor to authenticate as root, upload a binary, and change a security setting without first passing through vCenter role controls. Broadcom, the parent company of VMware, recommends managing vSphere through vCenter, disabling SSH during normal operation, and using Lockdown Mode where suitable. Required service accounts should be explicit exceptions rather than members of a broad administrator group.

Lack of enhanced security settings

The initial execution attempt was blocked by execInstalledOnly, but the attacker had enough privilege to disable this policy. Broadcom documents enforcement options that combine execInstalledOnly with UEFI Secure Boot and TPM-backed configuration protection. These controls must be enabled, tested, and monitored for change. A setting that can be silently disabled by the same credential used for daily administration provides limited resistance after account compromise.

Unsafe credential storage

Case 2 demonstrated the possibility of compromise lying in privileged credential exposure. The mitigation strategy involves not only securing the administrative credential storage but also general hardening practices of secret handling, such as privilege management and regular access audits.

How to close this attack path

In this section, we share remediation advice on how to mitigate such attacks, and detect and prevent them from going further. We recommend the following actions:

• Separate monitoring from administration. Create a dedicated monitoring identity for each platform and restrict it to the smallest set of objects and actions that the monitoring sensors require. Do not use ESXi root or another emergency account for routine polling. Prevent monitoring servers from starting interactive administrator sessions unless a separately approved support workflow requires it. The same principle applies beyond VMware.
• Replace stored root passwords. Locate every copy of hypervisor, management, storage, and backup credentials in monitoring tools, scripts, scheduled tasks, connection managers, and service configurations. Replace static passwords with vault retrieval, brokered identities, or limited API tokens where the platform supports them. Record every retrieval and rotate the secret after emergency use or compromise.
• Restrict direct host access. Route normal ESXi administration through vCenter and enable an appropriate Lockdown Mode after testing monitoring, backup, and recovery dependencies. Keep ESXi Shell and SSH stopped by default. When support work requires SSH, enable it for a defined period, restrict the source, and alert on service activation, root login, and changes to the exception list of users who are allowed to connect via SSH.
• Use a specialized security solution. In our portfolio, Kaspersky Cloud Workload Security (KCWS) is perfectly suited to address virtual environment risks, offering a powerful combination of two products: Kaspersky Hybrid Cloud Security (KHCS) and Kaspersky Container Security (KCS). Kaspersky Hybrid Cloud Security is specifically built to secure virtualized infrastructures, private data centers, and hybrid clouds. A patented Light Agent architecture minimizes resource impact without compromising performance, while comprehensive infrastructure visualization through a unified console gives administrators complete visibility and control over the entire hybrid network. Kaspersky Container Security covers every stage of a containerized app’s lifecycle, from development to operation. Among other capabilities, the solution allows for detecting misconfigurations using a dedicated scanner for images, file systems, and repositories that contain IaC files (such as Terraform, CloudFormation, Azure ARM templates, Helm charts, and Dockerfiles).
• Treat configuration changes as security events. Alert when execInstalledOnly, Secure Boot enforcement, Lockdown Mode, SSH, local accounts, exception users, firewall rules, or remote logging settings change. Baseline the expected state and test whether the security team can detect an unauthorized change. A secure configuration set once does not mean that the control remains active on the host.
• Isolate the management network. Place hypervisor, monitoring, backup, storage, and cluster administration on restricted management networks. Permit only the exact source and destination services required. Administrative workstations should enter through hardened jump hosts with named identities and multifactor authentication.
• Protect logs, backups, and recovery. Forward ESXi, vCenter, Proxmox monitoring, identity, and network logs to protected storage that a compromised administrator cannot erase. Backup platforms should use separate identities, restricted management paths, and recovery copies outside ordinary administrative reach.

Configuration checks for monitored virtualization

Below are recommended checks to run when enabling virtualization monitoring. The safest state depends on the platform and monitoring method, but each control should be tested.

The wider attack surface

Closing the monitoring and credential routes does not secure the environment by itself. Virtualization also relies on isolation boundaries, trusted images, management APIs, virtual networks, storage, and backups. Each layer requires a different control and leaves evidence in a different place.

VM and container escapes

In a VM escape, code inside a guest reaches past the VM boundary and affects the host or another guest. The weakness may be in a virtual device, an integration feature, a hypercall interface, or another component that translates guest requests for the host. If the escape works, control of one VM may lead to control of the physical server and every workload on it. VMware CVE-2025-22224 showed this risk: an attacker with administrator rights inside a VM could execute code as the VMX process on the host, and Broadcom reported exploitation in the wild.

A container escape can reach a similar result, but the starting point is different. Linux containers share the host kernel, so their isolation model differs from that of a VM. Namespaces limit what processes can see, cgroups control resource use, and capabilities split root privileges into smaller parts. A kernel or runtime bug can break this isolation. Copy Fail (CVE-2026-31431) is a good example of a kernel flaw. Code already running in a container could use a Linux AF_ALG crypto socket to change pages in the shared Linux kernel page cache. Because the host and other containers may read the same cached pages, the effect did not have to stay inside one container. The fix is a kernel update; Docker Engine 29.4.3 also tightened its default security profiles to reduce exposure on hosts that had not yet been patched.

Unsafe settings can also break the boundary. Privileged mode, excessive capabilities, writable host mounts, or access to the Docker socket may remove isolation without any software exploit. For instance, runc CVE-2024-21626 involved leaked file descriptors that could expose the host filesystem to a malicious image or container process.

This difference changes the investigation. A VM can often be treated like a separate computer with its own kernel, memory, and disk. A container is a group of host processes placed inside namespaces. If investigators collect only the container filesystem, they may leave the most useful process, socket, and control-plane evidence on the host.

Images and templates

A compromised golden VM image or container base image can spread through normal automation. Common weaknesses include unofficial public images, mutable tags, overprivileged build tokens, recoverable secrets in older layers, and stale templates that restore vulnerable software or forgotten accounts. Scanning might help, but it does not establish who built the artifact or whether the exact image tested and approved was the one ultimately deployed to production. Use controlled builders, provenance records, signature checks, and planned rebuilds from trusted sources.

Management tools and APIs

A stolen vCenter identity, exposed Docker API, overpowered Portainer role, or compromised backup console may give an attacker an easier route than an escape exploit. Portainer advisory GHSA-7fw3-x4r2-g7wc showed how a proxy validated one bind-mount representation but missed an equivalent API form, allowing an authenticated non-administrator with container creation privileges to reach host paths. The runtime performed a valid request after authorization had already failed in the management layer.

Administrative file-copy operations also deserve attention. Docker fixed archive and mount-handling flaws in CVE-2026-41567, CVE-2026-41568, and CVE-2026-42306. These cases required particular conditions and operator or API activity. They are a reminder to patch the daemon and record who initiated copy operations, which container was involved, the source and destination paths, and the result.

Virtual networks, storage, and backups

East-west traffic between virtual workloads may stay inside one host and bypass a physical sensor. Management, migration, storage, and workload traffic should use separate zones with filtering between them. Snapshot and memory files may contain credentials, while weak datastore permissions can expose whole virtual disks. Backup systems need broad access to recover services, which also makes them valuable to an attacker who wants to delete recovery points or reach several hosts.

Attack surface examples by layer

To sum up, the described attack vectors might be mitigated as follows:

Conclusion

GERT cases that we presented in this article did not require an attacker to break the VM boundary. The attack path was created by an overprivileged monitoring relationship, an insecure password storage approach, a recoverable and reused root credential, broad management-network reachability, and direct SSH administration. Each element was legitimate on its own, but together they allowed one compromise to reach virtualization hosts and their workloads.

Misconfiguration should therefore receive the same operational attention as vulnerability management. Teams need to know where privileged credentials exist, which systems can use them, which network paths make them effective, and which logs will show their use. Escape flaws, unsafe images, API weaknesses, virtual network exposure, and attacks on storage or backups remain serious, but closing the known administrative route should come first.

Executive summary

In 2025, several threat actors exploited CVE-2025-53770 and CVE-2025-53771 (ToolShell vulnerabilities) in on-premises Microsoft SharePoint to achieve remote code execution through crafted HTTP requests. One of the threat actors deployed ransomware on the target’s systems after successful exploitation. Microsoft attributed this ransomware-related ToolShell activity to Storm-2603, distinguishing it from other actors whose observed activity was primarily focused on credential theft, espionage, and data exfiltration.

In December, our retrospective analysis identified activity consistent with Storm-2603’s TTPs. This activity involved the attacker using the IIS worker process as an in-memory bridge to the customer’s infrastructure, keeping the access and control layer entirely within w3wp.exe without writing anything to disk. Although subsequent post-exploitation activity generated disk artifacts, the bridge used to maintain access remained memory-resident.

Let’s look in more detail at this attack.

The attack chain, from reconnaissance to infrastructure compromise

Intrusion timeline: Strategic latency and exploitation

The intrusion analyzed in this report occurred in two stages, with a temporal gap between initial access and subsequent exploitation activity. The attack timeline was as follows:

• Dec 20 – Vulnerability fingerprinting: A single HTTP request targeted a SharePoint administrative endpoint associated with the ToolPane component to determine whether the host was vulnerable to CVE-2025-53770.
• Dec 21-23 – Tactical latency: A three-day period of silence followed the initial probe, separating the vulnerability fingerprinting from subsequent malicious activity and potentially reducing the likelihood of immediate detection.
• Dec 24 – High-intensity re-engagement: On Christmas Eve, when security staffing at many companies is reduced, the full RCE chain was executed through the IIS worker process (w3wp.exe) on the same endpoint as the initial probe.
• Dec 26 – Incident discovery: The three-day gap initially prevented the December 20 probe from being correlated with subsequent malicious activity, marking the event as low priority. Retrospective analysis established that the probe was the initial phase of the subsequent intrusion.

Intrusion timeline

Initial access validation phase

Vulnerability fingerprinting

A vulnerability fingerprinting request on December 20 marked the first observed interaction with the target. The request originated from infrastructure associated with ONYPHE, an internet-scale attack surface discovery and management platform for identifying exposed assets, vulnerabilities, and cyberthreats. Unlike widely used tools such as Shodan and Censys, which merely provide a list of internet-facing assets correlated with the open-source data about known vulnerabilities, ONYPHE actually checks if the target system is vulnerable.

Fingerprinting with ONYPHE

The request characteristics were consistent with ONYPHE’s vulnerability checks, which use active, non-intrusive probes to identify internet-exposed systems vulnerable to specific CVEs. For ToolShell, ONYPHE adopted the approach used by Niels Hofmans (hazcod). Namely, it attempts to inject a harmless marker into the target server to find out if it is vulnerable.

OFFICIAL ONYPHE CVE CHECKER (TOOLSHELL)

This phase served as a validation step against the SharePoint execution surface exposed over HTTP:

• The target processed structured requests through the ASP.NET pipeline without rejection.
• The request path reached application logic capable of handling serialized input.
• No defensive controls interrupted or altered the execution flow at the application boundary.

Approximately 12 minutes later, a second inbound connection originated from infrastructure associated with Pfcloud UG, a provider operating under a bulletproof hosting (BPH) model. Given the timing and the IP’s documented history of scanning and abusive activity, the connection may represent follow-on reconnaissance against the newly identified target. No exploitation was attempted at this stage.

A connection from an IP address belonging to Pfcloud UG BPH

Active exploitation: Santa took your data and left a backdoor

The main malicious activity occurred on December 24. The actor targeted the same SharePoint host with a crafted request from 45.91.94.204 (45.91.92.0/22, ASN 63473, HostHatch, LLC). This resulted in a webshell execution within the IIS worker process (w3wp.exe). The payload was not written to disk; rather, it was loaded directly into the ASP.NET runtime and used during subsequent request processing. The implant remained resident for the lifetime of the affected application domain. This runtime state was lost when the application pool was recycled or IIS was restarted.

Attack originated from an SPN node

The IP address 45.91.94.204 is a Safing Privacy Network (SPN) node. SPN routes each connection through a multilayer VPN path with multiple relay nodes that can obscure the originating IP.

SPN promotes itself as a network that offers strong privacy protection for internet traffic. Its infrastructure resembles Tor’s in many ways, but with some differences. It features the following capabilities:

• Speed: Near-VPN performance for high-speed data transfer.
• Layer 3 support: Supports multiple protocols like TCP, UDP, ICMP (unlike Tor, which only supports TCP).
• App-routing: Direct tunneling without a browser.
• Multi-identity: Simultaneous exit nodes to bypass IP rate limits.
• Fixed-size packets and padding make it harder to analyze its traffic.

It is less common than Tor, and frequently bypasses standard Tor blocklists.

Webshell architecture

The webshell the attackers injected into the w3wp.exe runtime is a multi-module in-memory framework, where execution is orchestrated through the main component (G.cs) and extended via multiple functional units across namespaces.

The implementation follows a modular C# project structure in which each capability is isolated into its own compilation unit and invoked dynamically at runtime.

Webshell components

“G.cs” pipeline control and C2

Pipeline control

The main webshell component is G.cs. It orchestrates the implant’s execution context, lifecycle, C2 and session management.

To ensure persistence within the runtime, G.cs performs the following actions:

• Registers a custom VirtualPathProvider using the non-public RegisterVirtualPassProviderInternal method from the ASP.NET HostingEnvironment class so that ASP.NET uses it for virtual-path processing. The provider is automatically added to the chain of registered virtual path providers.
  
• Delegates the provider’s .NET Remoting lifetime policy to the previous provider in the chain, preserving the existing lifetime behavior.
  

Additionally, to evade defenses and enable the VirtualPathProvider to be registered even if the application in whose AppDomain the webshell is running is precompiled, the module implements the trust control subversion (T1553) technique:

• Uses reflection to check if the application is precompiled.
• Extracts pointers for internal state fields for the BuildManager class, which manages application compilation, and modifies them at runtime.
  
• Uses reflection once again to force runtime injection.

G.cs uses the GetCacheKey() function as the interception point for the virtual path processing flow. It processes incoming requests to the SharePoint server and checks their headers to filter out requests from the attacker.

The specific User-Agent in the request headers triggers the webshell execution. If the request doesn’t match this condition, the implant remains dormant, making its traffic harder to recognize.

Command and control layer (in-memory transport)

The same core module (G.cs) implements the communication layer.

Instead of relying on external frameworks or standard beacons, it uses a custom binary protocol with XOR-based obfuscation to exchange data with the C2. These communications blend into normal application traffic. The module uses the GetCacheKey() hook to intercept standard HTTP requests. When a specific User-Agent is detected in the request headers, the module parses it, extracts the payload, and establishes a TCP connection to a target host inside the target’s network if needed.

Bidirectional TCP tunnel initialization

G.cs establishes a full-duplex proxy tunnel to support interactive control. It stores active target sockets in memory to pair concurrent HTTP read and write channels.

TCP connections from the C2 server to arbitrary hosts inside the target network are supported for pivoting and lateral movement. The traffic is proxied through the SharePoint host.

Target-to-attacker data channel

Attacker-to-target data channel

As can be seen in the screenshots, the attackers used the suo5 tool to implement traffic proxying. Its authors promote it as a stable forward-proxying tool for scenarios where outbound internet connections are prohibited.

To increase its performance, G.cs manipulates ThreadPool by raising its limits for concurrent operations and maximum timeout.

ThreadPool manipulation

“Prog.cs”: Execution entry point and task dispatcher

Prog.cs is the entry point that receives command-line arguments and passes them to uk/London.cs. The latter acts as the orchestrator, handling command parsing and privilege escalation (via named pipe impersonation). We’ll review it in more detail later. If the “suo5” command is provided, London.cs triggers G.cs to hook into the ASP.NET runtime as a memory shell. Once active, G.cs independently processes incoming web traffic inside the web server memory.

Host interaction modules

The following modules provide direct system interaction capabilities, each implemented as a separate unit. London.cs triggers these modules when it receives a corresponding command from Prog.cs.

“FileDownloader.cs”

The FileDownloader.cs module downloads arbitrary files from external URLs provided by the C2. It stores the downloaded files in the Program Data directory without any user interaction.

“LoggedOnUsers.cs”

This module enumerates logged-on users and identifies their session types (interactive, service, remote). The results are stored in memory. The attackers can retrieve them using the proxy and tunneling capabilities provided by G.cs.

“ProcessList.cs”

This module lists running processes with full paths to the corresponding executables on the disk. The results are stored in memory and the attackers can retrieve them via G.cs.

“NetworkInfo.cs”

This module extracts information about existing network connections, including protocols, local and remote IPs and ports, and connection state. It also enumerates network interfaces and headers. The results are stored in memory and can be retrieved by the attackers via G.cs.

“MSI.cs”

This module silently installs and executes MSI packages previously downloaded by FileDownloader.cs.

“User.cs”

This module creates administrative accounts using the native SAM RPC subsystem (SAMRPCNative namespace) rather than standard command-line tooling. This may indicate an attempt to evade detection and provide the attackers with privileged stealthy access to target systems that persists after the webshell has finished its work.

SAMRPCNative

The SAMRPCNative namespace implements a low-level C# P/Invoke wrapper for the native Windows samlib.dll library, comprising three types: SAMStructs.cs, SAMMethods.cs, and SAMEnums.cs.

“SAMEnums.cs”

Implements structured bitwise lists and constant flags mapping numeric codes to their security meaning in SAM, and translates system status return codes.

“SAMStructs.cs”

Defines native data structures required for P/Invoke memory alignment and for marshalling. It securely formats and aligns data structures.

“SAMMethods.cs”

Contains external API declarations (P/Invoke) imported from samlib.dll to perform actions such as connecting to the SAM server, creating users and opening domains.

This layer is crucial for the attackers because it enables account operations.

Privilege escalation

The uk namespace contains offensive primitives for privilege escalation. To elevate privileges to SYSTEM, it uses a local token impersonation technique via the Encrypting File System Remote Protocol (EFSRPC) interface adopted from the EfsPotato tool.

This functionality is implemented in the uk/London class. It creates a malicious named pipe while the EfsrTiny class (a tiny version of the EfsPotato tool) connects to the LSASS.exe RPC server. Then it’s London.RpcThread function calls the EfsRpcEncryptFileSrv function from EfsrTiny with a crafted \\localhost path. This tricks LSASS.exe into connecting back to the attacker’s named pipe. Finally, the London.Exp function uses ImpersonateNamedPipeClient to coerce and impersonate the LSASS.exe token and spawn a new process via CreateProcessAsUser with SYSTEM privileges. As the webshell resides in the IIS worker process, it has the necessary SeImpersonatePrivilege to perform this technique.

The uk namespace also implements a minimal MSRPC client layer by explicitly defining structures such as RPC_CLIENT_INTERFACE and MIDL_STUB_DESC, thereby spoofing an interface stub. This enables direct interaction with the Windows RPC runtime (Rpcrt4.dll) without relying on MIDL-generated stubs or higher-level RPC abstractions. This provides direct control over binding and marshaling that goes beyond the constraints of standard client APIs.

Post-exploitation activity

Shortly after the webshell injection, the infected worker process spawned msiexec.exe to install a remote MSI payload hosted in Supabase cloud storage. The payload was Velociraptor, an open-source digital forensics and incident response tool – namely version 0.73.4.0 vulnerable to CVE-2025-6264 – that the attackers abused for command execution on the target network.

In October 2025, Cisco Talos reported Velociraptor being leveraged by threat actors as a post-compromise execution framework and attributed this activity to Storm-2603. This tool enables arbitrary command execution, and can be used for various purposes. In our case, it was used for persistence, discovery, data collection and payload execution.

The threat actor used Velociraptor to deploy multiple independent tunneling mechanisms, including Zoho Assist-Unattended Support for unauthorized remote access, VS Code CLI tunneling, Cloudflare Tunnel, and a lightweight reverse proxy utility. By doing so, they attempted to maintain access even if some of their tools were detected and deleted. At this stage, they also no longer depended on the IIS worker process lifecycle and ToolShell vulnerability.

EDR-killing attempts

Once the threat actor had access to the target system, they were able to upload a vulnerable driver that is used by many attackers to terminate EDR solutions. We were able to detect the main driver at C:\programdata\rsndispot.sys (054a32d6033b1744dca7f49b2e466ea2). In addition, the adversary used a malicious DLL (2d9ebf9c042f596f435865b40edad928) in a sideloading attack. This DLL was identified as Warlock ransomware’s AV killer. It was possibly intended to kill security solutions using the vulnerable rsndispot.sys driver.

Ransomware deployment attempt

The attackers made attempts to launch ransomware on the compromised system. However, the Proactive Defense Module in Kaspersky Endpoint Security blocked the ransomware process, effectively preventing this activity. The malware DLL we obtained was identified as Warlock ransomware.

What defenders really need to look for

ToolPane deserialization and CLR artifacts

When the attackers tried to access ToolPane, both the dynamically compiled App_Web_toolpane.aspx assembly and the Microsoft.GeneratedCode helper assembly were present within the same application domain.

Both assemblies are used in legitimate scenarios. App_Web_* assemblies are generated during normal ASP.NET page compilation, while Microsoft.GeneratedCode is typically produced by the XmlSerializer during legitimate serialization workflows. However, a request to the ToolPane endpoint that results in immediate loading of Microsoft.GeneratedCode within the same execution window indicates that the runtime is processing serialized data supplied through the request.

Detecting deserialization exploitation

First, it is highly recommended to read this article (in Russian) on how deserialization exploit attempts in the CLR should be detected, with examples of YARA rules and monitoring recommendations. A summary of the main idea of the detection logic is provided below.

Deserialization vulnerabilities should be treated as a distinct class of exploitation events. In the CLR, deserialization is not merely the conversion of bytes into values – it is the reconstruction of an object graph from an incoming stream. Serialization and deserialization are performed by formatters. One of the most widely used formatters is BinaryFormatter. It uses the NRBF format, which defines the stream as a sequence of records describing classes, arrays, primitives, and references between objects. The shape of the resulting graph is determined by the data supplied to the deserializer. This means that the input stream defines not only the values but also the specific types, relationships, and lifecycle points that the runtime must materialize.

Microsoft states explicitly that BinaryFormatter is unsafe and cannot be made safe; beginning with .NET 9, the in-box implementation is effectively removed from ordinary use. However, Microsoft continues to use it in its products, including SharePoint, because it is powerful and easy to use. To fix BinaryFormatter-related issues, architectural changes are needed. Similar warnings also apply to related unsafe mechanisms, including LosFormatter (used in the vulnerable page).

The primary risk of unsafe deserialization is that the CLR may resolve unexpected types, instantiate objects outside normal constructor invariants, and invoke special lifecycle mechanisms such as ISerializable, IObjectReference, IDeserializationCallback, and methods marked [OnDeserialized]. In other words, the attacker-controlled data can force the runtime to construct a graph containing types with executable side effects.

A practical detection strategy should therefore focus on graph-construction artifacts. CLR loader events identify the relevant assemblies and application domains. Memory and metadata inspection then reveal the type names and generated serializer structures associated with the suspected gadget chain. In ToolShell-like scenarios, unsafe deserialization usually produces helper assemblies (evidence in loader events) with metadata containing fully qualified type names, gadget class names, and string representations of the constructed generic types (just scan via YARA for it). In our case, the artifacts to look for include Microsoft.GeneratedCode, App_Web_toolpane.aspx* (evidence of deserialization in loader events) as well as strings identifying ObjectDataProvider, ExpandedWrapper, and LosFormatter (evidence that the input stream was deserialized into dangerous objects). Note that these indicators are not significant in isolation; their value lies in the fact that they show the runtime has already received data requiring helper code generation to reconstruct a dangerous object graph.

Gadget objects that exploit vulnerabilities like those associated with ToolShell are conveniently represented in corpus-style tooling such as ysoserial.net/YSoNet, which aggregate known gadget chains for unsafe .NET deserialization. For defensive purposes, the value of these projects lies not in their offensive capability but in the catalog of types and structures that can be searched for in streams, memory, and helper assemblies. The presence of any of them in memory or in a helper assembly should be treated as a strong indicator of exploitation.

To simplify deserialization exploit detection, we created a tool named CLRDeserializationExploitFinder. It can detect ToolShell exploitation attempts, as well as other gadget chains covered by ysoserial.net.

Detecting a VPP-based webshell/runtime implant

A mechanism based on VirtualPathProvider should be treated as a separate class of runtime implant (no files involved). In ASP.NET, HostingEnvironment.RegisterVirtualPathProvider registers a new virtual-path provider (VPP) in the application’s compilation system. Once registered, the application can serve virtual paths during dynamic compilation as though they were ordinary on-disk pages. Dynamic compilation does not require the payload to exist as a file in the filesystem. It operates entirely within the trust boundary of the application itself. During the compilation process, temporary files may be generated, but they cannot be treated as reliable forensic artifacts. Because VPPs can also be used for legitimate purposes, the defensive model should begin with an inventory of the legitimate VirtualPathProvider implementations. In all other cases, the registration or use of a new VPP should be considered anomalous.

To see how the dynamic generation of virtual pages using ASP.NET, IIS, and the CLR works, and to learn how to detect such activity, use our project VirtualPathProvider Lab.

The most useful telemetry source for this technique is the Microsoft-Windows-IIS-Configuration ETW provider. To detect virtual paths, events 25 and 47 are of primary value. Event 25 records the mapping of ConfigPath to PhysicalPath, and event 47 records the mapping of the configuration path to a directory. In the case of a VPP-backed path, these events create an inconsistency: IIS and ASP.NET behave as if the path has a physical representation, while the corresponding file does not exist on disk. In the example provided by VirtualPathProvider Lab, this appears as a mapping of the virtual resource googlecheck.aspx to a physical path where no real file is present. This discrepancy between configuration resolution and filesystem reality is the primary indicator of virtual content.

The second indicator is more negative than positive. For disk-backed files, IIS normally creates a FileChangeNotificationMonitor chain, as reflected in events 17, 18, 19, and 21. For virtual paths served by a custom VirtualPathProvider, this chain is absent or does not match the normal profile of an ordinary file because there is no physical object or corresponding on-disk change lifecycle. Consequently, the presence of positive events 25 and 47 combined with the absence of the expected events 17, 18, 19, and 21 for the same path forms a reliable detection pattern: the path exists for IIS as a configuration-resolved resource, yet it is not backed by the filesystem and is not accompanied by normal file-change monitoring.

To sum up, the hunting target here is the discrepancy between how IIS/ASP.NET resolves a resource and what is actually present on the disk and in the change-monitoring chain. For known applications, such cases can be filtered through an allowlist of legitimate VirtualPathProvider implementations. Anything else should be treated as a potential runtime implant and examined using ETW, filesystem verification, and memory inspection of the w3wp.exe process.

Attribution

Microsoft tracks Storm-2603 as a standalone threat actor with no known links to other groups. While they are careful about assessing the actor’s motivation, they mention that it has previously deployed Warlock and LockBit ransomware following active exploitation of on-premises SharePoint vulnerabilities. In the analyzed incident, we observed similar SharePoint exploitation activities, as well as an EDR killer associated with Warlock ransomware and unsuccessful Warlock launch attempts.

Other documented intrusions have identified Storm-2603 as leveraging known flaws within perimeter mail gateways to achieve initial access, subsequently staging the Velociraptor framework with elevated privileges and establishing persistent encrypted tunnels via commercial remote management software to orchestrate secondary lateral movement. This aligns with the post-exploitation behavior we observed in our case. Together with the ToolShell exploitation scenario, this allows us to attribute this case to Storm-2603 with moderate confidence.

Conclusion

From the incident analyzed in this article, the main defensive lesson is that exploiting an internet-facing SharePoint server can enable fileless code execution directly inside the application trust boundary. Storm-2603 did not require a conventional dropper, persistent service, or exposed C2 endpoint; instead, it deployed a webshell inside w3wp.exe, from which tunneling, privilege escalation, credential access, and lateral movement could be orchestrated. Detection therefore needs to move beyond file-based webshell hunting toward runtime behavior, such as anomalous w3wp.exe activity, unexpected outbound connections, RPC coercion, token impersonation, and the introduction of remote-management or DFIR tooling after application compromise.

To correctly attribute malicious activity and develop appropriate response measures, defenders should reconstruct execution chains and temporal relationships across application, host, and identity layers. They should also preserve memory and IIS telemetry, and correlate low-signal reconnaissance with subsequent privileged activity rather than evaluating events in isolation. A confirmed SharePoint exploit with code execution should trigger host-level containment, persistence hunting, credential and exposed MachineKey rotation, and TTP-driven investigation rather than remediation limited to the initial exploit or known IOCs.

Kaspersky products detect the threats mentioned in this article as:

• Trojan.MSIL.Agent.gen
• Trojan.Win64.DLLhijack.cdp

Indicator of compromise

A modern organization protects its information systems with a whole suite of technologies that generate thousands of security alerts every day. Looking at these alerts in bulk, you’ll see that a significant share are false positives. Ideally, these alerts would be filtered out automatically so that analysts could focus on the ones that may point to a real incident. However, writing filters is a time-consuming task in itself. To create a correct filter, an analyst needs to:

• Review the logs
• Identify the source of the activity
• Define filtering boundaries
• Choose filtering criteria
• Write a rule
• Check that the filter is robust

This post looks at how filter creation itself can be automated to reduce analyst workload.

Filter validity criteria

In the context of security alerts, a filter is a combination of event field values that marks a detection as a false positive and not worth the analyst’s attention. Filters can be generated for any combination of event fields, but not every combination yields a valid filter. That’s why we need to define validity criteria: conditions showing that a specific filter actually removes noise and doesn’t suppress useful alerts.

Detection rules in security systems typically contain a set of conditions, and each of them can generate an alert. A specific event triggers a given fragment of a detection rule. The set of events that a given fragment responds to is what we’ll call its context. A good filter should cover the entire context where possible, without going beyond it. Filters that are too broad or too narrow are useless. For example, a filter based solely on PowerShell would exclude too many events, including some that deserve the analyst’s attention. Most of the filtered events would also be unrelated to the rule in question. A filter on a specific ID, on the other hand, would cover only one event, which may never recur.

Problems in filter generation

We can run into a number of problems when creating filters. First, events often contain an excessive number of fields (around 400 on average), and most of them aren’t needed for filtering. At the same time, generating and ranking combinations of these fields is also fairly resource-intensive. So, the first step is to discard the irrelevant fields and keep only those worth using in the filter. For example, out of 400 fields in an event, four may be enough for filtering.

Another problem is string normalization. Field values (for example, the path to the same application on different systems) can vary depending on system settings, user folder names, and so on. For a filter to account for all these variations, the strings must be normalized. For file paths, in particular, you can replace the drive letter and user folders with standard environment variables and convert all paths to a single case.

Finally, if a filter completely mirrors the query of a detection rule, it effectively disables that rule. To fix this, remove the event fields used in the detection rule from the filter. For example, if a rule triggers on a file path, there are two ways to filter out unwanted alerts:

• In the filter, use fields other than the file path.
• Use a part of the file path that the rule doesn’t use. For example, for the rule file_path: ".../something.exe", you can set up a filter that excludes events with the user/unique_files/ directory in the file path.

Filtering security alerts with an algorithm

Given the problems described above, automatically generating filters for security alerts should consist of the following steps:

1. An analyst receives a security alert that they assess as a false positive and uses the filter generator.
2. The generator takes the 400-field event from the alert, along with the rule that triggered on it, and determines the context.
3. The generator selects the fields that are relevant to the filter.
4. The generator normalizes the strings.
5. The generator builds different combinations of the selected fields. To do this, we applied the FP-Growth (frequent pattern growth) algorithm to the context determined earlier. FP Growth builds a tree of frequently occurring items (fields) from a dataset (in our case, the context) and discards items that aren’t frequent enough. This reduces the number of combinations to check, which lowers the cost of finding the most relevant ones.
6. The generator ranks the resulting combinations and offers the analyst the top three to choose from.

For example, consider an event described by the following JSON:

After generating and ranking the combinations, we got three filters based on file paths:

• processcmdline:("nodejs\\node.exe" AND "*****\\appdata\\roaming\\npm\/node_modules\/pi-coding-agent\/dist\/cli.js")

• file_path:"*****/.pi\\agent\\bin\\fd.exe"

• processcmdline: "programfiles\\nodejs\\node.exe"

The last filter turned out to be too broad, but the analyst marked the other two as valid.

Pros and cons of the algorithmic approach

The algorithmic approach to filter generation has several advantages. First, it’s simple and deterministic: the same alert always produces the same result. Second, it’s interpretable, meaning we can see why a given combination ranked near the top of the list and why a particular field didn’t make it into the list of candidate fields at all. Third, the stages of the process are independent of each other, so individual steps can be improved and tuned without the risk of breaking the algorithm elsewhere. Finally, it has no external dependencies or models, which makes it easy to deploy in any customer environment.

However, it also has drawbacks. The first is its dependence on context. If there’s no context for some reason — for example, the rule’s first-ever trigger — a filter can’t be created. The second problem is string normalization. There’s a high chance of running into atypical cases that the normalization rules don’t cover. Often such cases can’t be described correctly at all, because they contradict each other.

These problems can be solved with large language models (LLMs). When an LLM generates the filters, no context is needed, because the LLM doesn’t iterate over or rank combinations. The LLM also takes a more flexible approach to string normalization, including non-standard cases. That said, an LLM doesn’t have to be involved at every stage of the generation process. We decided to keep the algorithmic solution where it works well. For example, a simple algorithm selects suitable fields without errors, so we didn’t move this stage to the model.

Filter generation with an LLM

The LLM-based filter generation looks like this:

The input is still an alert containing an event with 400 fields, plus the rule that triggered on that event. Then an algorithm selects the most suitable fields for the filter. Next, the LLM processes the input — the event, the selected fields, and the detection rule — and generates three filter options along with an explanation for them. The explanation helps the analyst understand why these particular filters were suggested and make an informed choice.

Consider the following event in JSON format:

The LLM suggested three filter options that all contain the same command line fragment:

• file_path: "\\WindowsPowerShell\\powershell.exe" AND filecmdline: "Get-VM -Name kafka\*"

• filecmdline: "Get-VM -Name kafka\*"

• filecmdline: "kafka*"

As in the previous example, two of the three output filters were valid. The last one was too broad to be usable. The analyst chose the first filter with minor edits:

file_path: "powershell.exe" AND filecmdline: "Get-VM -Name kafka\*"

Pros and cons of generating filters with an LLM

Using an LLM solved the problems of purely algorithmic filter generation: dependence on context and errors in string normalization. However, the single-request approach had its own drawbacks. First, it had no output validation. The LLM returned filters as-is, with no syntax check and no way to correct errors. Second, unlike in the algorithmic version, all filter generation tasks were handled by a single system prompt. As a result, a minor fix in one place could break the logic in another.

Using multiple AI agents

To address the problems of generating filters with a single model and a single system prompt, we tried distributing the tasks across different LLM agents. In this version, we brought in agents as early as the stage of selecting relevant fields. The chain includes four agents in total:

• Selector: selects the relevant fields.
• Generator: generates filters.
• Validator: evaluates the generated filters. If the filters are found to be invalid, it returns the task to the generator. If the selected fields are found to be irrelevant, it starts a new field selection cycle. If the filters pass validation, or the limit on regeneration attempts is reached, the valid filters (or the best ones available) are passed to the analyst.
• Commentator: analyzes the output filters and explains which field values were used and why.

For the following JSON event, the agents produce three valid filters based on the file path.

The filters differ in the additional parameters that support the detection:

• file_path:"sysvol\\domain\\scripts\\logon.bat"

• file_path:"sysvol\\domain\\scripts\\logon.bat" AND file_md5:"0x7..6E"

• autorun_entry: "Group Policy\\State" AND file_path: "SYSVOL\\domain\\scripts\\logon.bat"

Pros and cons of the agent-based approach

LLM agents give us a system that can validate and correct filters. Its modular architecture also lets us tune and improve different stages of generation independently. However, this approach makes more LLM calls than the previous ones, so the system is slower. It also depends on access to a model, which may not be available in the organization’s isolated environment.

Evaluating the filter generation system

To evaluate how well the filter generation system works, we use two main metrics:

• Approval rate. For each security alert, the system suggests three filters. If the analyst selects at least one of them, we count the generation as successful. For example, in the case below, the approval rate is 2/3.
  
• False positive reduction rate (FP drop). This metric shows how much a filter helps reduce the number of false positives. It can only be measured over time, because we need to compare the number of false positive alerts received during a set period before and after the filter is deployed.

Below is a comparison of the three filter generation approaches by these metrics:

As the results show, LLMs significantly improve the efficiency of filter generation. At the same time, the LLM agentless and agent-based approaches perform almost identically. So we chose the simpler and faster option: an LLM with a single system prompt. As a result, we cut false positives by 99%, increased the number of filters generated per day by 28%, and made analysts’ alert handling 17% more efficient.

Takeaways

Practice has shown that filter generation can be automated effectively. We’ve looked at several options for automatically generating filters for false-positive security alerts: a purely algorithmic approach, an LLM-based approach, and an approach built on a group of LLM agents. All of them can generate valid filters and make the analyst’s work much easier, but each has its own pros and cons.

The algorithmic approach scored lower on the evaluation metrics, but in two-thirds of cases, it still produces filters that satisfy the analyst. It works especially well when there’s already a set of similar events to filter out, meaning enough context has accumulated. The algorithmic generator can also be deployed in any environment. Both standalone LLM and multi-agent LLM approaches show high accuracy, and their results differ only slightly, so the slower agent-based approach looks excessive at this stage. If an LLM is available, the best option appears to be a single model that handles several stages of the generation cycle.

On October 27, Google issued a new Stable channel update for Chrome.

Most users are on Chrome’s Stable channel. The desktop update brings Chrome to versions 156.0.8078.73/.74 for Windows and Mac and 156.0.8078.73 for Linux. The update includes 52 security fixes, including four rated Critical.

On the same day, Mozilla issued Security Advisory 2026-118, which fixes 167 vulnerabilities. Firefox 159 also introduces several new features.

Both updates will roll out over the coming days and weeks.

How to update Chrome

The easiest option is to allow Chrome to update automatically. But you can end up lagging behind on updates if you never close your browser or if something goes wrong, such as an extension preventing the update.

If you don’t want to wait for the rollout to reach you, manually updating is easy. Open About Google Chrome from Chrome’s settings or Help menu. Chrome will check for updates. If one is available, click Relaunch to apply it.

You can find an explanation of the version numbering system and step-by-step instructions in our guide: How to update Chrome on every operating system.

How to update Firefox

To update Firefox, open the browser and click the menu button at the right side of the Firefox toolbar, then go to Help and select About Firefox. The About Mozilla Firefox window will open.

Firefox will automatically check for updates. If one is available, it will be downloaded. Once done, you’ll be prompted to click Relaunch. After Firefox restarts, it will be up to date.

Technical details

These Chrome and Firefox updates address a familiar problem: browser code mishandling memory while processing web content. Both releases fix use-after-free vulnerabilities, including flaws in page layout, JavaScript processing, and SVG graphics.

A use-after-free vulnerability occurs when a program attempts to access a memory location after it has been freed. That can cause crashes or, in some cases, allow an attacker to run their own code.

There’s another connection between these updates: both Google and Mozilla credit OpenAI Codex Security with finding bugs fixed in these releases. AI can help security teams examine browser code for weaknesses, alongside human code reviews and automated tests that check how software handles unexpected inputs.

Mozilla’s collaboration with Anthropic shows how AI-discovered findings can lead to fixes: researchers validated vulnerabilities before reporting them, giving Mozilla’s team reproducible bugs to investigate, repair, and deliver to users.

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Introduction

AI agents and associated tooling are becoming increasingly common in corporate infrastructure. Agents can perform a range of actions with the user’s privileges, such as accessing data, running commands, and interacting with external services. This creates new security risks, especially when these tools are used without the security team’s oversight or well-designed policies.

Detecting, tracking, and controlling AI agents is becoming one of the most pressing tasks for security teams today. We closely follow technological developments and continuously update our solutions to respond to new threats in a timely manner amid a rapidly changing technology landscape. This post describes new expertise built into Kaspersky products that helps counter the threats posed by the proliferation of AI agents. We approach this problem from several angles.

First, you need to thoroughly understand the threat you are dealing with. To this end, we added profiles to the Kaspersky Threat Intelligence Portal that describe various AI agents and how attackers exploit them. At their core, AI agents are programs (processes) that run in the operating system on endpoints and can also launch other processes. This means that Endpoint Detection and Response solutions are among the key endpoint controls for this threat. These solutions detect the presence and launch of AI agents, track their activity, and identify potentially dangerous behavior. When needed, they also take action, such as stopping a suspicious process, blocking the activity, or isolating the host, to reduce the likelihood of an incident escalating. For this purpose, we developed specially adapted detection rules.

You can use Kaspersky Endpoint Security, now also available as Kaspersky Next, to control and restrict the launch of AI agents. This solution uses two components to detect AI agents and control how they are used. Application Control categorizes the application processes launched on endpoints, and Web Control manages access to specific categories of web resources for users on endpoints.

Finally, even harmless AI agents can contain malicious instructions (skills), such as those downloaded from unsafe external sources. Kaspersky Scan Engine analyzes installed applications to detect these threats and also checks LLM files for malicious code. Let’s take a closer look at these solutions and technologies.

Popular AI applications and services in organizations

Tools from Anthropic and OpenAI take the top spots in the September 2026 ranking of AI agents by popularity among Kaspersky users. This list is based on telemetry from Kaspersky solutions. It shows the number of users who had the relevant AI vendors’ products installed at the time of the study.

The data shows that agentic systems, especially AI agents for software development, are the most popular AI applications. The TOP 10 also includes an application for running large language models locally (LM Studio) and a voice note-taking app (Wispr Flow).

According to open sources, these are the most widely used AI services in 2026:

While analyzing the most popular and widely used apps, our experts also noticed a sharp rise in vulnerable versions of AI-related software and services. From 2025 to date, more than 2500 vulnerabilities have been published:

Number of published vulnerabilities in LLMs, AI tools, and plugins with similar functionality, 2025–2026 (download)

* Data for previous quarters was updated and may differ slightly from previously published data.

Application Control and Web Control

To enforce the organization’s security policy for AI agents and other AI applications on the corporate network, Kaspersky products offer application control based on KL categories. These categories classify installed software and give you granular control over which approved applications can run in the organization.

Application Control analyzes the processes launched on endpoints, tracking which AI agents are running in corporate systems at any given moment, on which hosts, and under which accounts. Application Control also shows how long a given program has been in use.

This makes it easier for the Kaspersky Security Center (KSC) administrator to control applications. Administrators can use KL categories to allow or block AI agents inside the company for specific groups of employees.

Here is what this functionality looks like to KSC administrators:

KL categories available when configuring Application Control

For details on how to configure Application Control in KSC, follow this link.

In Kaspersky Endpoint Security (KES), Application Control can operate in two modes:

• Denylist. In this mode, Application Control lets users run any applications except those blocked by Application Control rules. This is the default mode.
• Allowlist. In this mode, Application Control blocks users from running any applications except those explicitly allowed by Application Control rules.

Below are the steps to configure Application Control to block AI tools.

Configuring Application Control for the AI Tools category in KES

With this setup, when a user tries to launch an AI agent, they get a notification and the agent doesn’t start.

KES notification about an attempt to launch an AI agent

For more on how to configure Application Control in KES, follow this link. Our public portal also lets you explore information on KL categories and the applications that fall under them, in particular details on how AI agents are categorized and how popular they are.

AI Tools KL category

The View applications drop-down list shows products for a specific vendor.

Similarly, Web Control lets you manage user access to web resources. If a user tries to open a denylisted website, KES blocks access and shows a warning.

KES notification about an attempt to access a prohibited web resource

When configuring access, the administrator can block websites that provide AI as a service.

Website categories

For more on configuring Web Control, follow this link. The help portal also provides information on website categories that can be assigned to resources to configure access control.

Kaspersky Endpoint Detection and Response

To an EDR solution, an AI agent is a regular process. It has its own executable, a tree of child processes, and network communications, all of which need to be monitored for suspicious activity. An attacker can use an AI agent as an automation tool. An AI agent installed as a legitimate user tool can also be leveraged in a ClickFix attack, where it executes a malicious instruction received from an untrusted source, such as a document, web page, or email. That said, unsafe actions by an agent do not always indicate an attack. There may be no malicious intent in the chain at all. An incident can result from what looks like an ordinary instruction from a user who doesn’t fully understand the consequences of having it executed. The mere fact that an agent was launched does not reveal whether it is being used in an attack. That is why Kaspersky EDR (KEDR) uses both conventional behavioral rules and rules written and adapted to detect AI tools. The latter identify risky agent actions and settings, and help determine which AI tool was involved in suspicious activity.

Conventional KEDR rules detect the vast majority of familiar malicious techniques, including when performed by an AI agent. A suspicious PowerShell launch, persistence via Task Scheduler, or an attempt to steal credentials leaves clear, identifiable traces. These traces look the same no matter what initiated the actions. The rules analyze launch parameters, process relationships, affected files, network activity, and other telemetry events.

For example, in a recent Armored Likho campaign, we found signs that AI had been used to create loader and dropper samples, which were later compiled with NSIS (Nullsoft Scriptable Install System). The key telltale artifacts were icons in the scripts and excessive comments on every function, which is uncharacteristic of human-written code. In addition, the group continues to generate new modules for its BusySnake Stealer and BusySnake RAT samples. For example, the attackers used AI to develop a module that runs multiple checks for virtual environment artifacts and calculates a score. Depending on the score, the sample either runs or exits with code 0. Even though the initial access samples, payloads, and their modules were AI-generated, the commands they execute via rundll32 and PowerShell are detected by the shell_creation_by_rundll32 and suspicious_powershell_cmd_or_script_spawning rules.

So, for detecting an attack like this, it is not important who wrote the loader, the payload, or its modules: they are given away by the commands they execute, process relationships, and other traces of activity in the system. AI can be involved both in preparing the code and in carrying out the attack directly on the device.

In the latter case, the attacker uses the agent to carry out their tasks and lets it choose and run the required commands within the privileges it has. For effective protection, it is critical to link suspicious actions back to the AI tool and the conditions under which it operates. In KEDR, several specialized rules handle this task.

We have created separate rules for popular AI agents, ai_agent_*_access_to_sensitive_file_**, where * is the tool name and ** is the operating system. They generate alerts when an agent accesses files that contain credentials, tokens, or keys.

ai_agent_opencode_access_to_sensitive_file_win Tap to previewTap to hide

The ai_agent_dangerous_execution_mode rule detects agents launched with auto-approval of all actions (so-called YOLO mode) or with the sandbox disabled. These settings do not indicate an attack on their own, but they let the agent perform dangerous actions without user confirmation.

ai_agent_dangerous_execution_mode Tap to previewTap to hide

The suspicious_mcp_server_artifact rule triggers when MCP server scripts are created or modified in hidden, temporary, or cache directories. Attackers can place an MCP server in these locations to quietly connect it to the agent: through the MCP server, they can pass instructions to the agent, call third-party tools, and access the user’s data.

suspicious_mcp_server_artifact Tap to previewTap to hide

The llm_api_access_by_unusual_apps rule generates an alert when an application on Windows, Linux, or macOS connects to the API of a known external LLM service, unless this activity falls under predefined exclusions. This helps spot model access by applications that do not normally behave this way.

llm_api_access_by_unusual_apps Tap to previewTap to hide

Some Kaspersky EDR rules tag events for investigation but do not generate alerts. For example, the ai_agent_**_execution rules flag launches of known agents on Windows, Linux, and macOS. The local_ai_model_artifact rule records the creation or modification of AI model files in typical application, runtime, and cache directories. These events reveal AI tools on the device, including tools that run on local models and never call an external API.

local_ai_model_artifact Tap to previewTap to hide

Kaspersky Threat Intelligence Portal

AI agent profiles

The Kaspersky Threat Intelligence Portal offers a large number of software profiles, including profiles of AI agents. You can sort them by the ai_ prefix:

AI agent profiles on Kaspersky TIP

The profile of an AI agent such as Claude Desktop includes a detailed description of the software, the privilege level required to run it, supported platforms, and threat actor groups known to use it. It also lists tactics and techniques mapped to the MITRE ATT&CK framework, with descriptions of the procedures the tool can be used for.

Claude profile on Kaspersky TIP

The description also lists ways to detect the software through standard system auditing mechanisms:

• Windows: events from standard audit logs and Sysmon events
• Linux: syscall audit events and Sysmon events
• Network auditing: a set of protocols and the traffic generated by the software

The detection section lists the main artifacts the software leaves in the system: command lines, possible launch parameters, names of the services and scheduled tasks it creates, and the key network artifacts.

Detection section in the Claude profile

Hunt Hub

In December 2025, the Kaspersky Threat Intelligence Portal added Hunt Hub (HH), a repository of detection rules. This is a unique Kaspersky project, and we developed it in response to growing market demand.

This functionality is available in the Threat Landscape section of the portal. It gives analysts access to detection rules: their descriptions and their mapping to MITRE ATT&CK tactics and techniques, as well as to the associated cybercriminal groups.

In the Hunt Hub section, customers can explore the detection logic of EDR, NDR, and NGFW products, including the logic for detecting AI agents.

Rules in the Hunt Hub repository

The rule card provides:

• Detailed description
• Rule’s severity level, confidence level, and alert format
• Detection tips
• Description of possible false positives
• Platforms the rule can run on
• Tactics, techniques, and sub-techniques covered by the rule
• Groups that use the technique covered by the rule
• Detection logic that shows what exactly triggers the rule

Detection rule card in Hunt Hub

Kaspersky Scan Engine

Skills are a key component of the AI agent ecosystem. They’re prewritten sets of natural-language instructions that extend agent functionality. We previously covered the risks that malicious skills pose to agent users. A skill can require the usage of additional programs and services, come with helper scripts (for example, written in Python), or contain a malicious command embedded right in the instruction text. This means that adding skills to an originally harmless AI agent opens up several new ways for malicious code to enter the system. To prevent this, any skills obtained from external sources must be scanned. Kaspersky Scan Engine is well suited for this task. This is a cyberthreat detection and response solution that seamlessly integrates with various applications. It can detect malicious code in agent skills, associated scripts, and in files generated by running agents.

Detection of a malicious agent skill in Kaspersky Scan Engine

Detection of an LLM with malicious code in Kaspersky Scan Engine

Conclusion

AI agents are rapidly making their way into corporate environments: they help employees work faster and take on a wide range of tasks, but they also open up new opportunities for attackers. To take advantage of this technology without compromising security, organizations need to build multi-layered protection and minimize risks. A range of Kaspersky solutions can help with this:

• Kaspersky TIP keeps you up to date on current scenarios in which attackers use AI agents, and its Hunt Hub section provides rules for detecting suspicious AI agent activity.
• Kaspersky EDR detects AI agents in the infrastructure and monitors their activity on endpoints. If it detects potentially dangerous actions, the product can log the event, notify the SOC, and take response actions, such as stopping the process or isolating the host.
• Application Control in Kaspersky products can fully restrict the use of AI agents within the company by using application categorization. The Web Control component can restrict access to AIaaS web resources.
• Kaspersky Scan Engine can be integrated into various company processes to detect malicious code in any files, including AI agent skills and LLMs.

When companies combine the tools described above in a comprehensive approach, they can adopt AI agents in an informed way: with an understanding of the associated risks and effective means of minimizing them.

Eight compromised eMudhra intermediate CA private keys risk unauthorized TLS signing and MitM interception. Read our analysis and containment guide.

The post EMudhra Intermediate CA Certificates Compromised appeared first on Unit 42.

A recently disclosed flaw in Signal’s calling software could allow another participant to keep hearing you after you hang up.

The vulnerability, tracked as CVE-2026-113380 (CVSS score 9.3 out of 10), affects RingRTC versions earlier than 2.72.0. RingRTC is the open-source library behind Signal’s voice and video calling functionality, providing calling components for its mobile and desktop applications.

The flaw concerns how Signal’s calling library shuts down a call. It does not affect how it encrypts conversations. According to the published vulnerability description, another participant could overwhelm a call’s internal event queue and interfere with the steps that should disconnect it when you end the call.

The main concern is unwanted listening after someone believes a conversation has ended. If a malicious call participant successfully triggered the flaw, they could potentially continue hearing audio that the other person no longer intended to share. That might include an offhand remark, a conversation with someone nearby, or other private background sound.

The vulnerability description also mentions that video might remain active, but does not confirm that behavior or explain what affected users would see on screen. It also doesn’t specify how long any continued transmission might last.

There are no known reports of exploitation in the wild. The vulnerability concerns only how a call is shut down. It does not involve stolen passwords, compromised accounts, or exposed message histories that would call for a password reset.

What to do

The developers updated the code to make shutdown more resilient when a call’s internal queue is full or another termination step fails.

Install any available Signal updates on your devices. The fix is available in the underlying RingRTC library, but the affected and first-fixed Signal app versions have not yet been confirmed publicly in the sources reviewed.

Personally, I found an update in the Google Play Store which brought my Android app to version 8.32.2. I did not find one in the Apple App Store, although this might be because I have automatic updates enabled. The current version on my iPad is listed as 8.32 (1910). While I think that means it’s all patched, this is hard to confirm from Signal’s website.

I’ve emailed Signal for clarification and will update this article when I hear back.

Scammers know more about you than you think. 

Malwarebytes Mobile Security protects you from phishing, scam texts, malicious sites, and more. With real-time AI-powered Scam Guard built right in. 

Here’s a counterintuitive truth: the ultimate goal of threat hunting isn’t to find more security incidents—it’s to drive continuous improvement across your entire security program. We’re not hunting merely to find present bad; we’re hunting to decrease the probability of future bad.

Think of it like debugging. You don’t debug just to find bugs—you debug to build better software. Each bug you find teaches you something about your system, improves your testing, and makes future bugs less likely. Threat hunting works the same way.

The Cyclical Nature of Threat Hunting

Every threat hunting framework can be thought of as a cycle that improves with every revolution.

Step 1: Determine Your Focus

The biggest challenge in threat hunting? Answering this question: “Where do we even start?” You can’t just randomly poke around in logs hoping to find something interesting. You need a method to focus your efforts.

The good news is that there are several effective approaches, and you don’t have to pick just one. In fact, most mature programs blend approaches over time.

Hypothesis-driven hunting starts with an educated guess, perhaps informed by the latest threat intelligence. Maybe something like, “I bet adversaries are using scheduled tasks for persistence on our web servers.”

Baseline hunting flips the question entirely: instead of rooting around for specific threats, you map what “normal” looks like in your environment, then investigate anything that doesn’t fit the pattern.

Statistical analysis tools like RITA let you approach those patterns from yet another angle. They surface statistically weird behaviors and connections, giving you a prioritized list of anomalies to consider and maybe investigate.

Machine learning models can highlight specific events that deviate from learned baselines, essentially saying “start here” with confidence scores attached.

Step 2: Investigation

The real detective work happens here. Investigation is iterative and rarely linear. You start broad, progressively narrow your focus by filtering out known-good activity, and follow interesting patterns wherever they lead. One scheduled task leads to a user account, which leads to authentication logs, which leads to source IPs, which leads to ... you get it.

The “art” is knowing which threads to pull and which to drop. Something can be technically anomalous but contextually benign, like a DBA running weird queries at 2 AM because production is on fire.

Step 3: Discovery and Analysis

Eventually you reach a conclusion. Maybe you found a threat. Awesome! Now hand it to incident response.

But maybe, or most likely in fact, you found nothing…

Here’s the critical mindset shift: finding nothing isn’t failure. It’s validation—discovery of a different kind, even. A thorough hunt might confirm that your defenses are working and that an attack isn’t happening (win!). Or it might reveal that a detection you thought existed doesn’t, or that it’s misconfigured and wouldn’t fire even if the attack happened (also a win because now you know what to fix).

Approached with this mindset, any outcome is a win, and every hunt ultimately makes you more secure.

Step 4: Knowledge Refinement and Improvement

This is where threat hunting transforms from investigation into force multiplication. Everything you’ve learned feeds back into your security program:

• Create detection rules so you don’t have to manually hunt for the same thing again.
• Document baselines about normal behavior in your environment.
• Share knowledge with your team and the wider community (Document!).
• Generate new hypotheses for the next hunt (Back to Step 1...).
• Close visibility gaps you discovered.
• Measure and communicate your program’s value.

This phase is what makes hunting a continuous improvement engine. Each excursion expands detection coverage, deepens environmental knowledge, sharpens hunting skills, and strengthens overall security posture.

The Self-Improving Loop

The real power of this hunting “loop” is its cumulative nature. Your first few hunts might feel slow and uncertain. But knowledge accumulates. Patterns become obvious. Investigation approaches become routine. Organizations committed to sustained hunting programs often hit critical mass around 12–18 months, where value accelerates dramatically.

Remember: You’re not just looking for today’s threats. You’re building tomorrow’s defenses. Every rotation improves your skills, the program, and the rotations themselves. That’s the threat hunting flywheel.

Security, Orchestration, Automation, and Response (SOAR) is still a foreign concept to some but has rapidly evolved into a necessity for high-performing SOCs. SOCs without a SOAR — or without meaningful automation — will struggle with manual repetition, duplicate alerts, and slow response times as they scale. With SOAR, many of these problems can be addressed or reduced.

While SOAR isn’t a “silver bullet” by any means, the operational impacts are real because of the power it gives a SOC to optimize workflows, centralize security alert management, and minimize threat response time (or mean time to resolution). According to the Ponemon Institute, organizations can receive on average upwards of 17,000 malware alerts per week. The BHIS Active SOC reduced overall ticket volume by roughly 60% through intelligent alert grouping — consolidating related signals into single cases instead of working them as individual alerts.

How SOAR Works

To understand how this is possible, we need to discuss what SOAR is and how it works. A SOAR is a platform specialized primarily around security use cases. This platform serves as a centralized hub for data enrichment, integrations, and response actions, all of which take place in the context of “playbooks.” Think of a playbook as a flowchart, where each step performs a specific operation.

At the top of the flowchart, data (let’s say an EDR alert) initially enters the playbook. As it continues, decision points control the directional flow, API requests gather additional data or perform actions, and finally, there is some sort of output. So, a SOAR is really a technology—a curated set of tools and processes that work together to automate what can be wisely automated so as to serve as a happy medium between total manual management and total automation to maximize a SOC team’s ability to respond quickly and appropriately despite the problems and time constraints that the team encounters due to sheer volume.

Real-World Application

Consider a real-world example: Suppose that a device triggers a low-confidence EDR alert. Since it’s low-confidence, the EDR doesn’t take any action and sends it to the SOAR. The SOAR makes an API call out to VirusTotal (a service for detecting malware) with the indicators of compromise (IOCs) of the alert. If the IOCs return as malicious, the SOAR reaches back to the EDR, which in turn, isolates the host.

Now let’s say that this EDR alert fired 100 times, each on a different signature, all on the same host. Let’s also say that network detections for Command and Control also started firing related to that user. With a SOAR, all of those disparate signals could be condensed into one singular Case, rather than a number of individual alerts. Using logic within your SOAR playbooks, you could group all these events together based on numerous field values, going a layer deeper than you normally could with a SIEM, which usually just allows for the suppression of duplicates.

Challenges of Implementing SOAR

Now that you understand the potential power of a SOAR, you might be asking, “Hayden, why isn’t everyone using a SOAR then?” There are a few good reasons for that:

1. A high price tag: While some offerings are maybe tens of thousands a year, some of the larger enterprise offerings could run you hundreds of thousands a year just to purchase the product.
2. Required expertise: A SOAR is a very powerful, but very delicate, tool. Used correctly, it could do the work of several FTEs for your team; used incorrectly, at best it may not work as you want, and at worst it could cause runaway scenarios of automated containment or remediation. Having qualified SOAR engineers on your team is critical to extract the true value of the technology.
3. Implementation effort: Even the most expensive SOAR won’t solve all your problems immediately. Like any technology, it will require maintenance and updates, but with a SOAR, you also have to build many of the functions that you need or at least cater them to your use cases.

The Bottom Line

It may sound like I’m trying to convince you that a SOAR isn’t worth the effort, but that couldn’t be further from the truth. On the contrary, SOAR is becoming an expectation for any high-performing SOC, rather than a nice-to-have. As volume and complexity of alerts increase, a SOAR becomes essential to respond quickly and adequately to these alerts.

Resources

• Ponemon Institute Report (“The Cost of Malware Containment”): https://www.ponemon.org/local/upload/file/Damballa%20Malware%20Containment%20FINAL%203.pdf
• How to SOAR in a SOC (Antisyphon Webcast): https://www.youtube.com/watch?v=YJC9dSgAjGw
• Hands-On SOAR: https://www.tines.com/blog/practical-security-orchestration-automation/

As AI becomes increasingly utilized throughout the security space, it's important to consider how it should be used most effectively. We've all seen companies adding AI into every offering and function they perform, often as much as possible.

In security operations, this creates a divide between two types of companies:

1. Companies that rely primarily on AI to do the work
2. Companies that enable their operators to become higher performers through the use of AI

Both types address a clear problem: volume. Anyone who has worked in a SOC knows that alert volume results in burnout, limits the number of customers you can support, and takes time away from more important tasks. Using AI to accelerate triage of high-volume, lower-complexity alerts is a practical and effective strategy. It frees analysts to focus on the ambiguous cases that require human judgment. With the right context and data, AI can meaningfully assist in distinguishing malicious from benign activity — but "most of the time" isn't good enough when a miss means a breach. AI augments the analyst; it doesn't replace their judgment.

That said, keeping a human in the loop is critical for the fringe cases: AI hallucination, highly complex technical investigations, and even situations where attackers attempt to fool the models with injection or evasion techniques.

Let's talk about some ways you can be the second type of company: the one that enables operators rather than replaces them.

AI for Triage Enhancement

Utilizing AI for enhancement of the triage process is something all security operation centers should be doing right now. While AI may occasionally be wrong or may hallucinate, anyone not taking advantage of it to work across the huge amount of data that SOCs process will fall behind their competitors.

I'm not suggesting that an AI model should be constantly closing alerts. Instead, consider this: Could an AI elevate alerts that would otherwise not have been investigated?

All SOCs process swathes of low-fidelity or low-severity alerts that are usually suppressed, deduplicated, or closed out through automation. What if you could use an AI model to review these alerts that would've been closed anyway and elevate those requiring human response to higher priorities? The worst-case scenario—a false negative—isn't applicable here. These alerts wouldn't have received much attention anyway. In the ideal scenario, you could intelligently review alerts your analysts wouldn't have looked at otherwise, escalating truly concerning activity for a human to look at.

AI for Quality Assurance

Another clear use case for AI in SOCs is quality assurance. Many QA checks on investigations are random, but what if you could curate a set of prompts that tasks AI with looking for common mistakes within your investigations and notifies a human to review them?

The AI could highlight the causes for concern, providing a starting point for the human analyst. It could even offer suggestions to both the reviewer and the analyst, making note of possible improvements. The higher quality the QA prompts, the better the feedback.

AI for Validation

Similar to the first use case mentioned, AI could validate analyst investigations and look for logical gaps or potential blind spots. Effectively, it could be used to provide top cover for analysts, giving them more space to triage quicker without chasing down every lead, knowing that the model (ideally trained on past cases!) is fact-checking and logically validating their investigation, freeing them to confidently triage without second-guessing themselves.

Human Augmentation

While AI excels at handling repetitive high-volume tasks, human expertise remains essential for complex investigations, fringe cases, and maintaining accountability. Rather than viewing AI as a cost-cutting tool to reduce headcount (or to take on many more customers with the same headcount), think of it as an investment that multiplies the effectiveness of your existing team. By strategically deploying AI to handle or fact-check routine work, you free your analysts to focus on the sophisticated threats that truly require human judgment and critical thinking.

If you take one thing from this article, I want it to be this:

Using AI to augment your operators may not show the same immediate "return" as replacing them, but, over time, it will increase your service quality tenfold.

Not every risky email should be blocked outright. Some messages may be legitimate but still deserve extra scrutiny. Until now, email security has largely followed a simple model: a message is either delivered or blocked. While this works well for clearly malicious emails, many modern attacks operate in a gray area where the risk is real, but not high enough to justify rejecting the message.

Cybercriminals have been relying on the same trick for years: hide malicious content where traditional email security tools cannot easily inspect it. Password-protected attachments, QR-coded URLs, and redirector-wrapped links have often acted as convenient hiding places for attackers. But it's possible to stop these threats.

Email hijacking remains one of the most effective techniques used by cybercriminals to conduct fraud, steal sensitive information, and impersonate trusted individuals.With new AI functionalities (dubbed "Anubis.AI") in our Mail Protection Service, we can stop such threats!

OpenAI’s latest containment failure adds to a pattern that may force the company to make an unpopular decision.

The company has paused training, evaluation, and tool-enabled inference for its most capable models after an internal research agent found a way around an intended internet restriction. More alarming, the agent remained active for hours after OpenAI’s monitoring system raised the alarm.

OpenAI published an account of the incident, which occurred during a search-based training task on September 20. According to OpenAI, the agent could not get useful results through its supplied search tools, tried direct access to search engines, and eventually tested the limits of its environment. It found that although direct web access was blocked, the sandbox’s DNS resolver could still reach the public internet. By using DNS delegation and a public chatbot that could respond through DNS records, the agent sent questions outside the restricted environment and received answers back. It subsequently sent 18 additional queries along the same route.

OpenAI’s misalignment monitor generated a high-priority alert within 15 minutes, and a human reviewer acknowledged it 3 minutes later. But the run did not stop automatically as expected. It continued for roughly another two and a half hours before someone stopped it manually.

OpenAI has not reported any exposure of sensitive data or compromise of an outside system in this incident. But it follows other disclosed cases in which agents went beyond their assigned tasks or crossed the boundaries of testing environments.

The New York Times reports that OpenAI agents also interacted with US government websites this summer without the company’s knowledge:

“OpenAI’s artificial intelligence went rogue and meddled with the websites for the Education Department, the Commerce Department and the Securities and Exchange Commission this summer without the A.I. lab’s knowledge, according to security researchers and a person familiar with the episodes.”

No breaches have been confirmed in those instances. And while Australia described the Medicare incident as unauthorized access, could it really be called an attack?

The call for an industry-wide slowdown has even prompted a lawsuit from paying subscribers who fear they would get less “value for their money.” Others worry that slowing down would give China a chance to pull ahead of the US in an increasingly tight technology race.

Here’s a thought: Why not accelerate the development of truly isolated testing environments? Better containment would make these tests safer and their results more reliable.

When a child isn’t ready to handle a dangerous object, you keep it out of reach. Why give an AI agent access it isn’t ready to use safely?

How to use AI agents safely

Treat an agent like an enthusiastic but fallible junior employee with access to your computer. Do not give it unrestricted access to your email, files, cloud storage, developer credentials, financial accounts, or production systems merely because it promises to save time.

Use separate accounts with minimal permissions. Keep sensitive data out of its working context where possible, require human approval before it sends messages, spends money, changes settings, or publishes anything, and regularly review its activity.

An AI agent does not need malicious intent to cause harm. A misunderstood instruction, an overly broad permission, or an unexpected workaround can be enough.

From reporting threats to removing them.

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

MacSync is a relatively young, rapidly evolving family of crypto/info stealers. First advertised on the dark web in 2025 as Mac.c, the stealer was later renamed to MacSync by its creators. The initial versions were implemented as AppleScripts and closely resembled the AMOS stealer family, but over time, MacSync developed distinctive features of its own, including a backdoor module. In this report, we discuss a new infection chain that differs significantly from previous variants. We first spotted it in the wild in September 2026.

Key points:

• The developers of this family have overhauled their approach to payload delivery by replacing script-based droppers with binary ones.
• The main malicious payload now consists of modules written in Objective-C and Swift.
• At one stage of infection, the attackers use iCloud to deliver the next

Kaspersky solutions detect the threats described below under the following verdicts:

• HEUR:Trojan.OSX.MacSync.*
• HEUR:Trojan-PSW.OSX.MacSync.*
• HEUR:Trojan-Dropper.OSX.MacSync.*
• HEUR:Trojan-Downloader.OSX.MacSync.*

Technical details

Infection chain

MacSync is an infostealer distributed under the malware-as-a-service (MaaS) model, so the specific delivery method for the first stage of the infection chain is up to the operators. Recent public reports on MacSync have mostly focused on modules delivered through social engineering and ClickFix-style attacks. However, both then and now, the malware has also spread disguised as free or cracked versions of popular applications, as well as under the guise of new software. For example, we found MacSync masquerading as a nonexistent crypto wallet app called Toria; the attackers not only created a dedicated web page for it but also promoted it on X and Telegram:

The latest version of the infostealer we discovered starts the infection chain with malicious DMG images. Even within a single campaign built around one fake application, we found two different ways the infostealer and backdoor modules were delivered to the victim’s device. In one, the payload inside the DMG was a compiled JXA script that, once launched, decoded a shell script and passed it directly to the interpreter without writing it to disk. In the other version of the application, the same script appeared at a later stage of infection, after a chain of droppers and loaders had run. We’ll take a look at the second infection chain in detail, since it is more complex and technically interesting. The infection scheme is shown below:

It’s worth noting right away that MacSync shows shared traits at almost every stage:

• All temporary files are placed in the /tmp directory. The same directory is where *.lock files are created to prevent the malware from running again.
• Once its task is complete, the module removes traces of its activity: temporary files, its own logs, and so on.
• All binary files are in the FAT Mach-O format and target devices with both Apple and Intel processors.

Loader, Calendar, and Two Simple Droppers

In this infection chain, the payload on the disk image is an .APP application. When started, it first checks whether the whole bundle has the com.apple.quarantine extended quarantine attribute, and if it finds one, it runs the xattr -cr <app_name> command to remove all attributes. Next, it extracts an XOR-encrypted URL from its overlay and decrypts it with the key 73 6f 6e 6f 6d 61 62 6c 64 07. After the encrypted data, there are 8 bytes indicating the length of the ciphertext, followed by the magic word SONOMAC1. It’s worth noting that the malware reads the overlay backwards: it first locates the magic word, then reads the data size, and then uses the size to determine the boundaries of the data block containing the ciphertext.

The resulting URL is a link to the next-stage downloader script. In some cases, this link pointed directly to a file hosted on an attacker-controlled server; however, in at least one sample, the link pointed to a public iCloud calendar:

hxxp://caldav.icloud[.]com/published/2/MTk1NDMwMDMzNTUxOTU0M1aHCZ-nMxiyGzBTzPiodOf44DtKJ6PpjftAG28_ui2NCYMpL_vu4pF4ddsJ8ysg0QI7pR0VEIEbZYdilVZRw08

Contents of the downloaded calendar

After retrieving the calendar file from the server, the downloader creates an anonymous pipe, launches the interpreter to read commands from standard input (zsh -s), sets the pipe as standard input, and redirects the contents of the calendar into it line by line. Since a calendar is normally not a command, the interpreter treats the lines as invalid commands until it reaches the malicious payload after the DESCRIPTION: line. These commands ultimately download a .TAR.GZ archive from iCloud that contains an .APP bundle. The downloader removes the quarantine attribute from it, signs it with an ad-hoc signature, and executes it.

We don’t know the contents of the scripts distributed from the attacker’s server, but they are very likely the same script found in the calendar event description.

The downloaded application is a dropper. The malicious payload it extracts is a zlib-compressed executable encrypted with AES in CBC mode, using the following key and initialization vector:

cb09ff86cabde4f8cee2d3cdec370c623bfa6c2b72ae9750fc9a7b299c65d7ca
3a1af2b397c6958e6c3ba3c75912d60e

The dropper decrypts and unpacks it, then places it at /tmp/.sys-<16-digit random value>.

Inside is another dropper, but unlike the previous stages, this one includes anti-debugging protection. In particular, it checks whether it’s running on a virtual machine by making sysctl queries with the kern.hv_vmm_present and machdep.cpu.brand_string parameters. It also sets the PT_DENY_ATTACH flag with ptrace to prevent a debugger from attaching to the process. The payload is a shell script encrypted with AES in CBC mode, using the following key and initialization vector:

3744f975113dfc552df982dcae699f9154a448e05a743bdfb641a463352bc13a
8d371f8a7a6dcc2655544ae13cbca03d

Payload of the second dropper

As shown in the screenshot above, the second dropper delivers a downloader script that retrieves the next-stage payload from the command-and-control server, decrypts it with AES in CBC mode using the following key and initialization vector, and then executes it in memory:

ff664112d3215c5d184689fc836e0dc6c1a47e42c34e70b2c3d356864bc4cb4c
09425f72de8bba18893dcd6f04115891

A couple more scripts

Inside the retrieved script, we can immediately spot several familiar indicators associated with the MacSync malware family:

• The main function in the script is named daemon_function.
• The stolen data is uploaded to the command-and-control server via PUT requests. The data in the requests is sent in 90-megabyte chunks. In earlier versions, the chunk sizes differed.
• One way to establish persistence on a system it uses is to inject a malicious command into the .ZSHRC, the configuration file for the ZSH interpreter, which contains commands that run each time the interpreter starts.
• The URL path where the backdoor executable is stored on the command-and-control server begins with the /loader/ directory.

The script performs the following tasks:

• Downloading and decrypting additional malicious modules: an infostealer, a backdoor, and a special utility for generating encryption keys and decrypting downloaded executable files
• Gaining persistence on the system
• Uploading data received from the infostealer module to the command-and-control server

One detail stands out: instead of the usual encryption algorithms (XOR, AES, and so on), the attackers took a different approach to delivering malicious modules at this stage. It involves a selfmade utility called pkgunpack that implements two commands: genkey and decrypt. The malicious payload is decrypted as follows:

1. The malware generates a public and private encryption key pair using genkey command from pkgunpack, whose generation function relies on an open implementation of the elliptic-curve Diffie-Hellman protocol on Curve25519: curve25519_donna.
2. The public key is encoded in base64 and sent to the command-and-control server together with a one-time code generated by the command $(date +%s)-${RANDOM}-$$.
3. The server responds with the following JSON:
   

   {
       "ok": true,
       "dek_wrap_b64":  <base64_encoded_encrypted_key> ,
       "build_pub_b64": "pFSxn/Uwg9bS45aVKCzA+8exSMfDHXpbpHC/f7G472w=",
       "crypto": "v2.5"
   }

   
   Here, build_pub_b64 is the server’s public key, which is also predefined in the script itself, and dek_wrap_b64 is a base64-encoded string that contains the payload encryption key. This key is encrypted on the server side with a shared secret computed from the public key generated with pkgunpack on the victim’s device.
4. Then decrypt command from pkgunpack utility decrypts the key:
   1. A shared secret is computed from the server’s known public key and the private key for the current session, using the same ECDH Curve25519 key exchange scheme that was used to generate the keys.
   2. The resulting shared secret is concatenated with the string sn-dek-wrap-v1, and a SHA-256 hash is computed from the result.
   3. Next, the dek_wrap_b64 block received from the server is decoded. It has the following structure:
      1. The first 5 bytes: additional authenticated data (AAD)
      2. The next 12 bytes: the initialization vector (IV)
      3. The rest: the ciphertext
   4. The ciphertext is decrypted with AES in GCM mode using the previously obtained key, IV, and AAD.
      

      Decoded dek_wrap_b64

5. The result is the key for decrypting the downloaded malicious payload. The payload, in turn, also contains an AAD and an IV in its header and is encrypted with AES GCM. The utility decrypts it and terminates.

Note that at each individual stage, the utility zeros out buffers after using encryption keys and data, apparently to impede forensic data collection and dynamic analysis of samples.

As mentioned earlier, at this stage, the script downloads only two modules: an infostealer and a backdoor. Once decrypted, both are .TAR.GZ archives; their contents are extracted, stripped of all extended attributes (such as com.apple.quarantine), and signed with an ad-hoc signature. The infostealer module runs first: it collects the data it needs, places it in a temporary folder, and compresses it into a .TAR.GZ archive, which the script then sends to the attackers’ server. Next, before launching the backdoor, the script sets up persistence for it and creates a backup copy. The backup copy, along with the other files it needs to operate, is placed in $HOME/Library/Application Support/System. This directory doesn’t exist in macOS by default; the script creates it. The backdoor disguises itself as the Finder application and achieves persistence in the system through the following methods:

• A LaunchAgent named com.apple.finder.agent
• Injection of a command that runs the .repair-run script when the ZSH interpreter starts from the .ZSHRC
• Injection of a similar command, which also runs the .repair-run script, into the global GIT pre-commit and post-checkout hooks

The .repair-run script checks whether the backdoor files exist, restores them from a backup if they are missing, and re-creates and reloads the LaunchAgent. At the same time, it kills the BTMNotificationAgent, NotificationCenter, and BackgroundTaskManagementAgent system processes to prevent the system from notifying the user about the new LaunchAgent.

One last thing worth noting about the script at this stage is its use of a custom HTTP header, X-Upload-Token, without which the C2 server responds to requests with errors. During our research, we observed the use of the following tokens: b8b4b88205a8f594b95a841bc37342898f34cad8a5a9e4a22ce69a31a1208650 and ff3ab9ef841630364818396f62e696b72aed162cf0b895b6643ef25dad79b51d. The backdoor later uses these same tokens to communicate with the C2 server.

Infostealer

The infostealer module ships as an .APP application, with its main executable written in Swift. As with previous AppleScript-based versions, the malware first asks the user for the administrator password. It adapts the window it displays to match the application it is impersonating. After the password is entered, the user sees a window that imitates a system notification about a corrupted application, offering to move it to the trash.

Fake stealer pop-up windows

Interestingly, instead of the method most macOS malware families use to verify a password, the dscl utility, the attackers used the Pluggable Authentication Modules (PAM) API. This is a fairly new technique for macOS malware, first observed in the wild in July 2026 in the Pam Stealer family. It apparently caught the attention of malware authors, and we may see it used more often going forward.

Password verification with PAM

Many strings in the stealer (file names, directory names, team IDs, and so on) are XOR-encrypted and stored in static arrays. The encryption keys differ between samples and are generated based on the ciphertext length.

String decryption

The set of data the stealer collects has expanded slightly compared to previous versions. The generalized list is as follows:

• Browser data: browsing history, cookies, crypto wallet extension data, saved logins and passwords, and Local State files
• Crypto wallet application data
• Telegram data
• Device login and password
• Keychain file
• System information: list of installed applications and running processes, device model, hardware, UUID, and so on
• Configuration files for SSH, ZSH, AWS, Kubernetes, GIT, and other services/programs
• ZSH and Bash command history
• Current user profile picture

The collected data is saved to a hidden directory in /tmp/.

The stealer module also has one interesting feature, disabled in all samples discovered so far and apparently still in development. Its purpose is to check whether the malicious application’s resources contain a file called KcHelper at <app_path>/Contents/Resources/Helpers, and, if the file is present, launch it with certain parameters. If this file is missing, a fallback function, _kc_grab_storage_item, is executed instead. Since KcHelper was not present among the application’s resources at the time of our research, we can only speculate about its purpose based on our analysis of this function. It first runs a command that modifies the partition_id of the keychain entry for a specific service so that three categories of applications can access it without user confirmation and without the keychain password:

• teamid: the application is signed with a certificate that has a specific teamID (in this case, the target application’s developer)
• apple: the application is an Apple service
• apple-tool: the application is an Apple command-line utility

security set-generic-password-partition-list -a <account_name> -s <service_name> -S <application_groups> -k <keychain_password> <keychain_path>

The stealer then uses the Security.framework API to try and retrieve the secret’s contents on its own, which still ends up triggering a confirmation request for the operation. It appears the threat actors plan to refine this feature in the future to gain unimpeded access to secrets even if the keychain password changes, but at this point, they haven’t managed to do so, which is why the feature is disabled. In the stealer’s encrypted strings, we saw examples of arguments for the command that modifies partition_id, which indicate that the attackers are after browser secrets. Example:

Chrome Safe Storage|Chrome|ChromeStorage|apple-tool:,apple:,teamid:EQHXZ8M8AV
Brave Safe Storage|Brave|BraveStorage|apple-tool:,apple:,teamid:KL8N8XSYF4

Code section responsible for changing access to keychain services

Backdoor

The backdoor is a Fat Mach-O executable written in Objective-C. It has two launch modes: a regular one and one with the --persist-status flag. In the second mode, it only checks how it was added to the persistence objects: as a Login Item or as a LaunchAgent. In standard mode, before proceeding to its main functionality, the backdoor also checks whether it has been added to autorun in any way. If not, it uses the same persistence mechanism as the parent script. However, for macOS versions older than 13.0, a separate helper executable stored inside the backdoor’s body is used regardless of whether autorun objects are present. The helper performs a single task: it uses the CoreServices.framework API to add the executable file passed to it as an argument to the Login Items.

As with the droppers from the early stages of the infection chain, the configuration for communicating with the C2 is stored in the executable’s overlay and encrypted with XOR using the same key. It consists of several strings separated by null bytes:

• AGNT1: a magic constant confirming that the configuration was decrypted correctly
• C2 server URL
• Access token: the same one used in the parent script
• BLD-150: the backdoor build number

The malware also writes logs to $HOME/Library/Logs/.sysnotif-agent.log and supports extended logging when launched with the LAUNCHER_DEBUG environment variable. Communication with the C2 takes place over HTTP. The server’s response should be a JSON file.

Although the backdoor offers several different commands, they all boil down to the same action: extract the base64-encoded AppleScript script from the script_b64 field in the server’s response and execute it. Individual command handlers then act as wrappers around the scripts, correctly populating telemetry and sending requests to the C2 server. Based on the command names and the messages sent to the server during their execution, we can reconstruct their purpose without having the scripts on hand. The backdoor supports the following commands:

• deploy_ext: deploy an extension downloaded from the server into the victim’s browser.
• deploy_ledger: replace the installed Ledger wallet with the version from the server.
• regrab: collect system information and/or specific files again. This time, the collected data is packaged into an archive typical for the MacSync family, at /tmp/osalogging.zip, unless a different path is specified in the archive_path field sent along with the command.
• live_browser: the only command executed without an AppleScript script. The backdoor checks for the presence of the sn_relay file among its resources, and if it’s not found, downloads and executes it. Its content and purpose remain a mystery to us, but based on the command name and the messages sent to the server, we can assume that the attackers somehow implement a MitM attack on traffic originating from the victim’s browser.

The section of the regrab command where the archive’s integrity is verified and its hash is calculated before it is sent

Takeaways

The new version of the MacSync infostealer differs quite significantly from its previously observed variants. The attackers have substantially overhauled their approach to executing the stealer’s and backdoor’s main malicious payload, moving from AppleScripts to full-fledged executable files written in Swift and Objective-C. It’s also worth noting the more complex infection chain: instead of obfuscated shell scripts delivered through ClickFix attacks, this version used binary droppers and loaders, some of which leveraged Apple’s infrastructure as one of the intermediate stages for delivering the malicious payload.

The nature of the data attackers seek to collect from a victim’s device, as well as the categories of applications the stealer disguises itself as, clearly indicates that this malware family primarily targets developers, crypto enthusiasts, and other users associated in some way with IT and the crypto space. MacSync’s compromise of software developers’ devices poses particular security risks for both end users and corporate systems, opening up expanded opportunities for attackers to further their intrusion.

Indicators of compromise

Stage one loader
26a0f7cdb9f7dc5ace9a40af825b1538
2d69812584269699fade26622e6490c5
7df1049cbd56c0bfa4a3364a379b4c2c
9f15fe9c4415cd668334339f705b94d8
fb90887592655a8c989e443c640167aa
6791dad263cac6d63ebba6a4b57e7d71

Malicious calendar (stage two)
3ded1d71a822b53b12c3b67bcaf633f5

Stage three dropper
781ce50001d4b449600afa347c9b0208
8e84b01d5ac9624f0b181ade0e737193
980e2134679bc0c609f7659882883d77
4203ec932bfcc0907f91732440d6d997
eb760d5c88f13f7ee0f8f86ba3407123
f9f70096aabb4d22a6657014f4853a53

Stage four dropper
3deeed48fd38f22e369f5c3092bd68a1

Stage five script
f97d24212fa6a21be0c4d211e10f044c

Stage six script
00d12d842596bf5ee1805effb4571d30
9a0043d900a9ac78c886c59c9a328fd0

Auxiliary .repair-run script
7212229c85852c3bffaf9740002b2f39

Infostealer
c53d0ea45dbc622afb7f16ea3eec78bc

Backdoor
fc3ba5ed282d77127efd0b0f2403531b

Auxiliary autorun tool
8dc8561349d144d4661bc66f2ec49f9f

URL
hxxps://toria[.]app/
hxxps://warpcast[.]asia/Toria.dmg
hxxps://streamyard.appstore.com[.]mx/installer.sh
hxxps://slack.apple03cloudstore[.]com/installer.sh
hxxps://toria.apple03cloudstore[.]com/
hxxps://waaako.appstore.com[.]mx/installer.sh
hxxps://toria.apple03cloudstore[.]com/e3c1a6b00bc31e14/stage2.enc hxxps://docsend.appstore.com[.]mx/dcc737d157ef4271/stage2.enc
hxxps://docsend.appstore.com[.]mx/dcc737d157ef4271/CoreUpdate.pkg.enc
hxxps://docsend.appstore.com[.]mx/dcc737d157ef4271/Helper.pkg.enc
hxxps://caldav.icloud[.]com/published/2/MTk1NDMwMDMzNTUxOTU0M1aHCZ-nMxiyGzBTzPiodOf44DtKJ6PpjftAG28_ui2NCYMpL_vu4pF4ddsJ8ysg0QI7pR0VEIEbZYdilVZRw08
hxxps://gateway.icloud[.]com/caldav/1_MTk1NDMwMDMzNTUxOTU0M0pybtJB186GzhogprwCQUjY3oZNiDFHH8WVo6bmgUtI/attach/4GE4TKNBTGAYDGMZVGUYTSNJUGOAALDAFMDOJBGWNUCYJLZRNDCLCO2YMQ3I64RLGMNXVG3KYBPWQOGYIEI7MPBDDYHECFDYVENTXIYFNDCPOVRMCTYI236RCYZAE63V5U3RTUYGUMO2CO7PKCLWMCXE73M7OPTHSGRWH5DXQ4PCUQU4ELZTLW54JSTK2H7VQ6PD26WOA2R7PPIQ6RTJWDEWP34U3HB4YWMXXC6EJ6PKWILSPYRSDEVY6QGMWSIUN6PR5W35KO3D4QZE7CFPUVBAEKI/Loader.app.tar.gz/YXR0YWNoYXR0YWNoYXR0YRhrE8mQ0E-b_dTUSGStQgTQ0ULFxCanei3Ke-EuEyQL

C2
hxxps://docsend.appstore[.]com[.]mx
hxxps://toria.apple03cloudstore[.]com