PseudoSigner01PEProtect09Anorganix

Hunt Hypothesis

This detection identifies potentially malicious PE executables exhibiting suspicious code signing characteristics associated with the Anorganix threat actor, specifically targeting pseudo-signed binaries that may evade standard signature validation. A proactive hunt is essential in Azure Sentinel to uncover stealthy initial access or lateral movement attempts where adversaries leverage forged certificates to bypass trust mechanisms and establish a foothold within the environment.

YARA Rule

rule PseudoSigner01PEProtect09Anorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 52 51 55 57 64 67 A1 30 00 85 C0 78 0D E8 07 00 00 00 58 83 C0 07 C6 90 C3 E9 }

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 5 specific false positive scenarios for the PseudoSigner01PEProtect09Anorganix detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Defender Antivirus Signature Updates

  • Context: The MpCmdRun.exe process frequently downloads and installs new definition signatures. These updates often contain PE (Portable Executable) files with embedded signatures that may exhibit structural anomalies or “pseudo-signing” characteristics similar to the Anorganix detection logic, particularly during off-hours automated scans.
  • Filter/Exclusion: Exclude processes where ProcessName equals MpCmdRun.exe and CommandLine contains /Update. Alternatively, filter by ParentProcessName = MsMpEng.exe to isolate engine-initiated updates from user-triggered ones.

• Scenario: SCCM (System Center Configuration Manager) Application Deployment

  • Context: During scheduled application deployments or patching cycles, the SCCM client (ccmsetup.exe) extracts installer packages to temporary directories. These extracted installers often utilize third-party packaging tools that generate PE files with non-standard header structures, triggering the rule when the deployment agent executes them in a sandboxed environment.
  • Filter/Exclusion: Create an exclusion for ProcessName = ccmsetup.exe or wuauserv.exe running within paths containing \Microsoft\CCM\. Additionally, exclude events where the file hash matches known SCCM deployment package hashes stored in a whitelist database.

• Scenario: Adobe Acrobat Pro Automated PDF Generation

  • Context: Enterprise workflows often involve background services (e.g., AcroRdrDC.exe or Acrobat.exe) generating large batches of PDF documents for reporting. The internal rendering engine creates temporary PE executables with specific digital signature chains that the YARA rule may misinterpret as ”