PEArmor07600765hying

Hunt Hypothesis

This rule identifies potentially obfuscated or packed Windows executables that may be used to hide malicious code from static analysis, a common tactic for initial access or privilege escalation. Proactively hunting for these artifacts in Azure Sentinel helps detect stealthy payloads that traditional signature-based detections might miss, ensuring early identification of suspicious binaries in the environment.

YARA Rule

rule PEArmor07600765hying
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 00 00 00 00 00 00 00 00 [4] 00 00 00 00 00 00 00 00 [8] 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [12] 00 00 00 00 4B 45 52 4E 45 4C 33 32 2E 64 6C 6C 00 00 00 00 47 65 74 50 72 6F 63 41 64 64 72 65 73 73 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 00 47 65 74 4D 6F 64 75 6C 65 48 61 6E 64 6C 65 41 00 00 00 00 00 08 00 00 00 00 00 00 00 60 E8 00 00 00 00 }

condition:
		$a0
}

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

• Legacy .NET Framework Application Updates: When an older internal line-of-business application (e.g., a custom inventory management tool written in C# targeting .NET Framework 4.0) is updated via a silent installer or msiexec, the resulting binary may retain specific PE header characteristics or resource strings that match the heuristic signature.

  • Filter/Exclusion: Exclude files located in the specific application directory (e.g., C:\Program Files\InternalTools\InventoryApp\) if the executable name matches InventoryService.exe and the file size is within the expected range (±10% of the known good version).

• Scheduled Backup Agent Execution: Enterprise backup solutions like Veeam or Commvault often use lightweight PE agents that are signed but may be compiled with specific linker settings that trigger generic PE armor checks. If the rule flags the backup agent binary during its scheduled 2 AM run, it is likely a false positive due to the agent’s static linking or specific section alignment.

  • Filter/Exclusion: Exclude processes where the parent process is the backup service (e.g., VeeamBackupSvc.exe or cvp.exe) and the file path resides in the standard backup agent directory (e.g., C:\Program Files\Veeam\Backup and Replication\).

• Java Native Interface (JNI) Helper Libraries: Some Java applications (e.g., Jenkins, Tomcat, or custom microservices) load native helper DLLs or EXEs for performance tuning. These binaries are often compiled with specific GCC or MSVC flags that result in PE structures matching the rule’s criteria. This frequently occurs during application restarts or when new plugins are installed.

  • Filter/Exclusion: Exclude files where the parent process is a Java runtime (e.g., java.exe or javaw.exe) and the file extension is .dll