MSLRHv032afakePEtite21emadicius

Hunt Hypothesis

This rule identifies potentially malicious or obfuscated code patterns within memory or files, suggesting an adversary is attempting to hide their presence or execute custom payloads. Proactively hunting for these signatures allows the SOC team to detect early-stage intrusions or low-fidelity malware that may evade traditional signature-based detections in the Azure Sentinel environment.

YARA Rule

rule MSLRHv032afakePEtite21emadicius
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B8 00 50 40 00 6A 00 68 BB 21 40 00 64 FF 35 00 00 00 00 64 89 25 00 00 00 00 66 9C 60 50 83 C4 04 61 66 9D 64 8F 05 00 00 00 00 83 C4 08 EB 05 E8 EB 04 40 00 EB FA E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 50 E8 02 00 00 00 29 5A 58 6B C0 03 E8 02 00 00 00 29 5A 83 C4 04 58 74 04 75 02 EB 02 EB 01 81 0F 31 50 0F 31 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF }

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 PE header manipulation tool (such as pefix or peb from the PE-b library, or a custom Python script using pefile) to strip debug sections or fix corrupted headers in a native C++ application binary before deployment.

  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\dev\, C:\work\) or exclude processes known to be build tools (e.g., msbuild.exe, cmake.exe, python.exe) that are writing to .exe or .dll files in source control directories.

• Scenario: An IT administrator uses a commercial or open-source binary patching tool (like HxD in hex-edit mode, or a specialized tool like PE Patch) to apply a hotfix or license key patch to a legacy application executable that lacks a proper update mechanism.

  • Filter/Exclusion: Exclude file paths containing keywords like patch, hotfix, or legacy in the directory name, or exclude files modified by processes with names like hxd.exe, patcher.exe, or admin_tool.exe.

• Scenario: A security team or QA engineer uses a fuzzer or mutation tool (such as AFL++ or angr) that generates mutated PE files in a temporary workspace directory to test application robustness against malformed headers.

  • Filter/Exclusion: Exclude files located in temporary directories (e.g., %TEMP%, C:\fuzzing\, C:\qa\) or exclude files with extensions other than .exe/.dll if the rule is overly broad, or specifically exclude paths containing fuzz, test, or qa.

• Scenario: A software installer or updater (such as `Inno