AHTeamEPProtector03fakePCGuard403415FEUERRADER

Hunt Hypothesis

This hunt detects adversaries attempting to evade endpoint protection by masquerading legitimate processes as fake PC Guard utilities using specific YARA signatures within Azure Sentinel. Proactive hunting for this behavior is essential to identify early-stage evasion tactics that may bypass standard signature-based defenses and prevent potential lateral movement or data exfiltration.

YARA Rule

rule AHTeamEPProtector03fakePCGuard403415FEUERRADER
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 90 [46] 90 FF E0 FC 55 50 E8 00 00 00 00 5D EB 01 E3 60 E8 03 00 00 00 D2 EB 0B 58 EB 01 48 40 EB 01 }

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 detection rule AHTeamEPProtector03fakePCGuard403415FEUERRADER, along with suggested filters and exclusions:

• Scenario: Legitimate deployment of Microsoft Defender for Endpoint (MDE) protection updates via Group Policy.

  • Context: The YARA rule likely flags the signature or behavior of the MsMpEng.exe process when it downloads or installs a new “PC Guard” style definition update, which mimics the structure of the targeted fake protector. This often occurs during scheduled maintenance windows (e.g., 02:00 AM daily).
  • Suggested Filter/Exclusion: Exclude the specific file path C:\Program Files\Microsoft Defender\MsMpEng.exe from the rule scope, or add a condition to ignore alerts where the parent process is svchost.exe (specifically the DefenderSvc service) during standard maintenance hours.

• Scenario: Execution of third-party patch management tools (e.g., Ivanti Neurons or SCCM).

  • Context: Tools like Ivanti or Microsoft Configuration Manager often deploy security agents that include a “PC Guard” component to verify endpoint integrity before applying patches. The YARA rule may misinterpret the installation package or the agent’s self-protection mechanism as the specific fake protector signature defined in the rule.
  • Suggested Filter/Exclusion: Create an exclusion for processes spawned by IvantiService.exe or ccmsetup.exe. Additionally, filter out alerts where the process command line contains keywords like “PatchDeployment” or “IntegrityCheck”.

• Scenario: Scheduled antivirus definition updates from enterprise-grade AV solutions (e.g., Symantec Endpoint Protection or Carbon Black).

  • Context: Enterprise AV suites often run background tasks to update their own