MSLRHv032afakePESHiELD025emadicius

Hunt Hypothesis

This rule targets the presence of a specific YARA signature associated with a fake PE shield or obfuscation technique, indicating potential attempts to hide malicious code or evade static analysis. Proactively hunting for this low-severity indicator allows the SOC team to identify early-stage reconnaissance or low-and-slow intrusions that may not yet trigger high-fidelity alerts, ensuring visibility into subtle adversary behaviors within the Azure Sentinel environment.

YARA Rule

rule MSLRHv032afakePESHiELD025emadicius
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 2B 00 00 00 0D 0A 0D 0A 0D 0A 52 65 67 69 73 74 41 72 65 64 20 74 6F 3A 20 4E 4F 4E 2D 43 4F 4D 4D 45 52 43 49 41 4C 21 21 0D 0A 0D 0A 0D 00 58 61 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 build engineer uses a custom C/C++ compiler (such as GCC or Clang) to compile a small utility or test harness that includes the PE header structure definition or uses a library that embeds a minimal PE shield for debugging purposes. The resulting binary contains the specific byte sequence or structural pattern targeted by the YARA rule, triggering a false positive during file integrity scanning.

  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\Dev\Projects\, D:\Builds\) or files with extensions .obj, .lib, and .a from the YARA scan if they are known to be intermediate build artifacts. Alternatively, add an exclusion for files owned by service accounts used by CI/CD pipelines (e.g., svc-ci-build).

• Scenario: An IT administrator deploys a custom PowerShell script or a small C# tool to patch or inspect PE headers on Windows endpoints for compliance auditing. The tool itself, or the temporary files it creates during execution, may contain the specific “fake PE shield” pattern as part of its logic or data structures, causing the detection to fire on the host where the tool is running.

  • Filter/Exclusion: Create a whitelist for known administrative tools by their SHA256 hash or specific file paths (e.g., C:\AdminTools\PEInspector.exe). Additionally, exclude temporary directories like C:\Temp\ or %TEMP% for files that are less than a certain size (e.g., < 50KB) to avoid catching small utility scripts or their transient outputs.

• Scenario: A scheduled task runs a third-party backup or snapshot utility (such as Veeam, Acronis, or a custom in-house solution) that creates memory dumps or file snapshots of running applications. If the application being snapshotted has a PE