MSLRHv032afakePELockNT204emadicius

Hunt Hypothesis

This detection identifies potential adversary activity involving fake PE (Portable Executable) locking mechanisms that may indicate early-stage file integrity tampering or evasion tactics. A proactive hunt is essential in Azure Sentinel to uncover stealthy threats that manipulate executable structures before they trigger higher-severity alerts, ensuring the SOC team can investigate subtle anomalies indicative of sophisticated malware behavior.

YARA Rule

rule MSLRHv032afakePELockNT204emadicius
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB 03 CD 20 C7 1E EB 03 CD 20 EA 9C EB 02 EB 01 EB 01 EB 60 EB 03 CD 20 EB EB 01 EB E8 03 00 00 00 E9 EB 04 58 40 50 C3 EB 03 CD 20 EB EB 03 CD 20 03 61 9D 83 C4 04 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

Here are 5 specific false positive scenarios for the MSLRHv032afakePELockNT204emadicius detection rule, which targets fake PE headers and potential Emsisoft/Malware behavior in a Windows environment:

• Scenario: Automated Endpoint Protection Scans (Emsisoft Emergency Kit)

  • Context: The Emsisoft Emergency Kit or the standard Emsisoft Antivirus engine performs deep heuristic scans on compressed archives or executable bundles. During this process, the scanner may temporarily inject a fake PE header into memory to analyze file integrity without fully loading the original binary structure, triggering the YARA rule’s “fake PE” signature.
  • Filter/Exclusion: Exclude processes matching emsisoft.exe, emscan.exe, and their child processes from the detection scope. Additionally, add a path exclusion for the installation directory: C:\Program Files\Emsisoft\.

• Scenario: Microsoft Defender Antivirus Real-Time Protection

  • Context: When Microsoft Defender scans large .zip or .7z archives containing nested executables, it often creates temporary virtual PE structures in memory to inspect the contents. This behavior mimics the “fake PE lock” signature defined in the rule, particularly when scanning files within the C:\Windows\Temp directory during off-hours maintenance windows.
  • Filter/Exclusion: Create a filter to ignore alerts where the parent process is MsMpEng.exe and the file path contains \AppData\Local\Microsoft\Windows Defender\.

• Scenario: System Center Configuration Manager (SCCM) Software Deployment

  • Context: During scheduled software deployments, SCCM uses the ccmsetup.exe agent to unpack application packages. The deployment engine often generates temporary stub executables with modified PE headers to verify installation prerequisites before executing the main installer, which can