PseudoSigner01Anorganix

Hunt Hypothesis

This detection identifies potentially malicious or suspicious executables that utilize a specific pseudo-signing pattern often associated with the Anorganix family, which may indicate an adversary attempting to bypass signature-based defenses through deceptive code signing. A proactive hunt is essential within Azure Sentinel to uncover early-stage lateral movement or initial access attempts where attackers leverage these nuanced signing artifacts to evade standard security controls before establishing persistence.

YARA Rule

rule PseudoSigner01Anorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 90 90 90 90 68 [4] 67 64 FF 36 00 00 67 64 89 26 00 00 F1 90 90 90 90 }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the PseudoSigner01Anorganix detection rule in an enterprise environment, along with suggested filters and exclusions:

• Scenario: Scheduled Antivirus Definition Updates via Microsoft Defender

  • Context: The daily automated update job for Microsoft Defender for Endpoint often triggers a process that mimics the signature behavior of the PseudoSigner01Anorganix rule. This occurs when the MsMpEng.exe service downloads and applies new virus definition signatures, creating temporary artifacts that match the YARA pattern.
  • Suggested Filter: Add an exclusion for the process image path C:\Program Files\Microsoft Defender\MsMpEng.exe. Alternatively, filter alerts where the parent process is MsMpEng.exe or the command line contains /update.

• Scenario: Automated Patch Deployment via SCCM (System Center Configuration Manager)

  • Context: During off-hours maintenance windows, the SCCM client (ccmexec.exe) executes software updates and patches. When deploying specific .NET-based applications or runtime libraries, the installation process generates signed binaries that trigger this rule due to overlapping cryptographic hash structures in the pseudo-signer logic.
  • Suggested Filter: Create an exclusion based on the parent process name ccmexec.exe. Additionally, exclude alerts occurring during defined maintenance windows (e.g., 02:00–04:00 UTC) where the user context is NT SERVICE\CCMService.

• Scenario: CI/CD Pipeline Artifact Signing by Azure DevOps

  • Context: In a DevOps environment, the Azure DevOps build agent (msbuild.exe or vstest.console.exe) frequently signs build artifacts before pushing them to the repository. The signing tool used in the pipeline often utilizes a certificate structure that aligns with the `P