PEtitevxx

Hunt Hypothesis

This rule detects the presence of the PEtitevxx YARA signature, which typically identifies specific malicious or suspicious executable files that may indicate a foothold for initial access or lateral movement. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify compromised endpoints or unmanaged assets before the adversary can leverage the file for further exploitation or privilege escalation.

YARA Rule

rule PEtitevxx
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B8 [4] 66 9C 60 50 }

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: A developer or sysadmin uses 7-Zip or WinRAR to create a compressed archive of a large source code directory or log files. The resulting .zip or .rar file contains multiple small executable files (e.g., .exe, .dll) or scripts, which may trigger the “PEtitevxx” heuristic if the rule flags mixed content or specific PE headers within the archive structure.

  • Filter/Exclusion: Exclude files with extensions .zip, .rar, .7z, .tar, .gz from the detection scope, or limit the rule to files with standard executable extensions (.exe, .msi, .dll) only.

• Scenario: An IT administrator runs Sysinternals Suite tools (e.g., Process.exe, PsExec.exe) or Chocolatey package manager to install or update software. These tools often spawn child processes or write temporary PE files to disk that may match the “PEtitevxx” signature due to their specific compilation structure or embedded resources.

  • Filter/Exclusion: Whitelist known benign paths such as C:\Program Files\Chocolatey\, C:\Sysinternals\, or C:\Windows\Temp\ for specific user accounts (e.g., DOMAIN\svc-admin), or exclude processes with known parent images like 7z.exe, powershell.exe (when invoking specific scripts), or choco.exe.

• Scenario: A scheduled maintenance job runs Microsoft Update or WSUS client services, which download and temporarily stage .cab or .msi files containing PE executables in C:\Windows\SoftwareDistribution\ or C:\Windows\Installer\. The “PEtitevxx” rule may flag these temporary staging files if they are scanned before being fully integrated or cleaned up.