PCGuardforWin32v500SofProBlagojeCeklic

Hunt Hypothesis

This detection identifies the presence of a specific Win32 variant associated with PCGuard software, potentially indicating legitimate application activity or an initial foothold for supply chain compromise. Proactive hunting is recommended to validate the legitimacy of this artifact across endpoints and distinguish it from potential masquerading malware that mimics trusted security tools within the Azure Sentinel environment.

YARA Rule

rule PCGuardforWin32v500SofProBlagojeCeklic
{
      meta:
		author="malware-lu"
strings:
		$a0 = { FC 55 50 E8 00 00 00 00 5D 60 E8 03 00 00 00 83 EB 0E EB 01 0C 58 EB 01 35 40 EB 01 36 FF E0 0B 61 B8 [3] 00 EB 01 E3 60 E8 03 00 00 00 D2 EB 0B 58 EB 01 48 40 EB 01 35 FF E0 E7 61 2B E8 9C EB 01 D5 9D EB 01 0B 58 60 E8 03 00 00 00 83 EB 0E EB 01 0C }

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 PCGuardforWin32v500SofProBlagojeCeklic detection rule, along with recommended filters and exclusions:

• Scenario: Microsoft Defender Antivirus Real-Time Protection Scanning

  • Context: The MsMpEng.exe process frequently scans executable files in the %ProgramFiles% directory. If the YARA rule matches a specific byte pattern or string signature found within standard Windows system binaries, it may trigger during routine background scans initiated by the Microsoft Defender service.
  • Filter/Exclusion: Add an exclusion for the process path C:\Program Files\Windows Defender\MsMpEng.exe and exclude file paths under C:\ProgramData\Microsoft\Windows Defender\.

• Scenario: Scheduled System Patching via WSUS or SCCM

  • Context: During nightly maintenance windows, the Windows Update service (usoc_dla_service) or Configuration Manager client (ccmexec.exe) downloads and installs updates. These processes often extract temporary .msi or .cab files that contain the specific headers or strings targeted by the rule, causing alerts during the extraction phase.
  • Filter/Exclusion: Exclude process names usoc_dla_service.exe, ccmexec.exe, and wuauserv.exe. Additionally, filter out events occurring between 01:00 AM and 05:00 AM on weekdays if this aligns with your maintenance window.

• Scenario: Enterprise Endpoint DLP Agent File Monitoring

  • Context: Data Loss Prevention (DLP) agents such as Symantec DLP or Forcepoint often monitor file creation and modification in user directories (C:\Users\). When a user saves a document that triggers the agent’s policy engine, the agent may spawn child processes or create