PEtitev13

Hunt Hypothesis

This rule detects potential malicious or suspicious Portable Executable (PE) files that match specific structural or behavioral characteristics defined by the PEtitev13 YARA signature, often indicative of obfuscated payloads or known malware families. Proactively hunting for these artifacts in Azure Sentinel allows the SOC team to identify low-severity threats that may have been missed by standard signature-based detections, ensuring early containment of stealthy intrusions within the environment.

YARA Rule

rule PEtitev13
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 66 9C 60 50 8D 88 ?? F0 [2] 8D 90 04 16 [2] 8B DC 8B E1 68 [4] 53 50 80 04 24 08 50 80 04 24 42 }

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

• Scenario: Execution of the dotnet CLI tool (specifically dotnet.exe or dotnet-*.dll) during a continuous integration/continuous deployment (CI/CD) pipeline or local developer build process. The YARA rule PEtitev13 often targets specific .NET assembly headers or resource sections that are standard in modern .NET Core/5+ applications, causing legitimate build artifacts to match.

  • Filter/Exclusion: Exclude processes where the parent process is cmd.exe, powershell.exe, or msbuild.exe and the file path contains \bin\ or \obj\ directories, or explicitly whitelist dotnet.exe if it is located in the standard SDK installation path (e.g., C:\Program Files\dotnet\).

• Scenario: Execution of the git command-line tool (specifically git.exe or its helper git-remote-https.exe) during automated repository synchronization or scheduled backup jobs. Some YARA rules targeting PE files with specific section names or import tables can inadvertently match the static libraries or helper executables bundled with Git for Windows, especially if the rule checks for generic Windows API imports common in Git’s C++ backend.

  • Filter/Exclusion: Exclude processes where the file path matches C:\Program Files\Git\ or C:\Users\<User>\AppData\Local\Programs\Git\, and the parent process is powershell.exe, cmd.exe, or a scheduled task service (svchost.exe with TaskScheduler context).

• Scenario: Execution of the python interpreter (specifically python.exe or pythonw.exe) when running scripts that utilize C-extension modules (like numpy, pandas, or cv2) which load native .pyd or .dll files. If the