PELockv106

Hunt Hypothesis

This rule detects the presence of the PELockv106 YARA signature, which identifies specific malicious or suspicious Portable Executable (PE) files that may indicate compromised binaries or low-level memory manipulation tools. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify stealthy artifacts that traditional network-based detections might miss, ensuring early discovery of potential footholds within the environment.

YARA Rule

rule PELockv106
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 00 00 00 00 00 00 00 00 [8] 00 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 56 69 72 74 75 61 6C 41 6C 6C 6F 63 00 4B 45 }

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

• Antivirus/EDR Self-Scanning and Update Cycles: During scheduled full system scans or post-update integrity checks, security agents like CrowdStrike Falcon, Microsoft Defender for Endpoint, or Trend Micro Apex One may load their core engine DLLs into memory. If the YARA rule targets generic PE header structures or specific import tables common in these large, complex binaries, the agent’s own process (e.g., FalconSensor.exe or MsMpEng.exe) can trigger the alert.

  • Filter/Exclusion: Exclude processes where the parent process is a known security agent (e.g., FalconSensor.exe, MsMpEng.exe) or where the image path resides in standard vendor directories (e.g., C:\Program Files\CrowdStrike\, C:\Program Files\Microsoft Defender\).

• Legacy Java Runtime Environment (JRE) Initialization: In environments running legacy enterprise applications (e.g., SAP GUI, Oracle Forms, or IBM WebSphere) that depend on older versions of the Java Runtime Environment (JRE 7/8), the java.exe or jvm.dll components often exhibit PE characteristics that match generic “lock” or “header” patterns in YARA rules. The JVM’s native code loader may create temporary PE structures in memory that resemble the rule’s signature.

  • Filter/Exclusion: Exclude alerts where the process name is java.exe or javaw.exe and the parent process is a known application server or client (e.g., sapgui.exe, websphere.exe), or filter by image path containing \jre\ or \java\.

• Visual Studio and .NET Toolchain Compilation: When developers or CI/CD pipelines run Microsoft Visual Studio (e.g., devenv.exe) or **