PseudoSigner02ASProtectAnorganix

Hunt Hypothesis

This hypothesis targets the execution of binaries signed with the ASProtect packer, a tool frequently leveraged by adversaries to obfuscate malicious code and evade signature-based detection. Proactively hunting for these artifacts in Azure Sentinel helps identify low-severity, potentially stealthy implantations that may serve as initial access vectors or persistence mechanisms before they escalate in impact.

YARA Rule

rule PseudoSigner02ASProtectAnorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 90 90 90 90 90 90 5D 90 90 90 90 90 90 90 90 90 90 90 03 DD }

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

• Legacy Application Deployment via Group Policy

  • Scenario: An IT administrator deploys a legacy line-of-business application (e.g., an old inventory management tool) that was compiled using the ASProtect packer to reduce file size. The binary is copied to the C:\Program Files\LegacyApp\ directory via a GPO software installation policy, triggering the YARA rule on the client machines.
  • Filter/Exclusion: Exclude files located in C:\Program Files\ or C:\Program Files (x86)\ where the parent process is gpupdate.exe or svchost.exe (specifically the gpclient service), and the file extension is .exe or .dll.

• Third-Party Antivirus/Security Tool Updates

  • Scenario: A security vendor (e.g., CrowdStrike, SentinelOne, or a niche EDR provider) releases an update for their agent or a companion tool (like a memory scanner or log collector) that uses ASProtect for packing. The update service downloads the new binary to a temporary directory (e.g., C:\ProgramData\Vendor\Updates\) and executes it to replace the old version.
  • Filter/Exclusion: Exclude files where the parent process is the vendor’s update service (e.g., vendorupdate.exe, csagent.exe, sentineloneagent.exe) and the file path contains ProgramData or AppData\Local associated with the security vendor’s directory structure.

• Scheduled Backup Agent Maintenance

  • Scenario: A backup solution (e.g., Veeam, Commvault, or Acronis) runs a scheduled maintenance job at 2 AM. The agent’s helper utility (often a small, packed executable used for disk scrubbing or metadata verification) is executed from a specific