PEtitev21

Hunt Hypothesis

This rule targets specific executable file characteristics associated with the PEtitev21 YARA signature, indicating the presence of a known or suspicious binary artifact that may be used for initial access or payload execution. Proactively hunting for this indicator allows the SOC team to identify dormant or low-noise malware instances in Azure Sentinel before they can establish persistence or escalate privileges within the environment.

YARA Rule

rule PEtitev21
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B8 [4] 6A ?? 68 [4] 64 FF 35 [4] 64 89 25 [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 DevOps engineer uses a legitimate static analysis or binary inspection tool (e.g., Ghidra, Binary Ninja, or PE-bear) to analyze a custom-compiled microservice or third-party library. These tools often load and parse PE headers in memory, which can match the structural or string-based patterns of the PEtitev21 YARA rule if it targets specific section names, import tables, or entropy levels common in debug builds.

  • Filter/Exclusion: Exclude processes where the parent process is known analysis tools (e.g., ghidra.exe, bnd.exe, pe-bear.exe) or where the image path resides in standard development directories (e.g., C:\Program Files\Ghidra\, C:\Users\<User>\AppData\Local\Programs\BinaryNinja\).

• Scenario: An enterprise application (e.g., Adobe Creative Cloud, JetBrains IDEs, or Visual Studio) loads a large number of native plugins or extensions that are compiled with specific linker settings or contain debug symbols. If PEtitev21 targets specific section names (like .debug$S or unusual section alignments) or high entropy in specific sections, these legitimate plugin DLLs may trigger the rule during startup or hot-reload events.

  • Filter/Exclusion: Exclude images where the file path matches known vendor plugin directories (e.g., C:\Program Files\Adobe\Adobe Creative Cloud\, C:\Users\<User>\.vscode\extensions\, C:\Users\<User>\AppData\Local\JetBrains\) and the process name matches the host application (e.g., devenv.exe, code.exe, photoshop.exe).

• Scenario: A scheduled maintenance job runs a legitimate backup or snapshot utility (e