PGMPACK v013 additional

Hunt Hypothesis

This hypothesis targets the presence of the PGMPACK packer, a tool frequently used by adversaries to compress and obfuscate malicious payloads to evade static analysis and signature-based detection. Proactively hunting for this indicator in Azure Sentinel allows the SOC to identify potentially compromised endpoints or suspicious artifacts that may be leveraging this specific packing technique to hide their true intent.

YARA Rule

rule PGMPACK_v013_additional: PEiD
{
    strings:
        $a = { FA 1E 17 50 B4 30 CD 21 3C 02 73 ?? B4 4C CD 21 FC BE ?? ?? BF ?? ?? E8 ?? ?? E8 ?? ?? BB ?? ?? BA ?? ?? 8A C3 8B F3 }
    condition:
        $a 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

• Scenario: A developer or DevOps engineer is compiling a large C++ or Java application using a build tool that utilizes the PGMPACK compression algorithm for resource embedding or executable packing to reduce size.
  • Filter/Exclusion: Exclude files located in standard build output directories (e.g., C:\Projects\*\build\, C:\Users\*\AppData\Local\Temp\build\) or exclude processes initiated by known build tools like MSBuild.exe, javac.exe, or cmake.exe.
• Scenario: An IT administrator is deploying a legacy line-of-business application that was originally packaged with PGMPACK v0.13 to maintain compatibility with older Windows versions, and the installer or the final executable is being scanned during a routine patching or deployment cycle.
  • Filter/Exclusion: Create an allowlist for specific known legacy application executable names (e.g., LegacyApp.exe, OldSystemCore.dll) or exclude files in the C:\Program Files\LegacyApp\ directory if the application is verified as trusted.
• Scenario: A security team is performing a manual malware analysis or reverse engineering task in a sandboxed environment or a dedicated analysis workstation, where a sample known to be packed with PGMPACK v0.13 is being executed or inspected.
  • Filter/Exclusion: Exclude detection on specific analysis workstations (by hostname or IP range) or exclude files in the designated malware analysis directory (e.g., C:\MalwareAnalysis\Samples\) to prevent noise during active investigation.
• Scenario: A third-party vendor-provided utility or plugin (e.g., a specific PDF converter, image editor, or database tool) is installed on user machines, and its core executable or DLL was packed with PGMPACK v0.13 by the vendor to protect intellectual property or reduce