EncryptPE2200461622006630WFS

Hunt Hypothesis

This rule detects the presence of a specific PE executable that has been processed by an encryption or packing tool, a technique often employed by adversaries to obscure malicious code and evade static analysis. Proactively hunting for these encrypted binaries in Azure Sentinel allows the SOC team to identify potentially hidden payloads or trojans that may be executing on endpoints before they trigger more advanced behavioral detections.

YARA Rule

rule EncryptPE2200461622006630WFS
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 9C 64 FF 35 00 00 00 00 E8 7A 01 00 00 00 00 00 00 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 [36] 00 00 00 00 6B 65 72 6E 65 6C 33 32 2E 64 6C 6C 00 00 00 47 65 74 53 79 73 74 65 6D 44 69 72 65 63 74 6F 72 79 41 00 00 00 43 72 65 61 74 65 46 69 6C 65 41 00 00 00 43 72 65 61 74 65 46 69 6C 65 4D 61 70 70 69 6E 67 41 00 00 00 4D 61 70 56 69 65 77 4F 66 46 69 6C 65 00 00 00 55 6E 6D 61 70 56 69 65 77 4F 66 46 69 6C 65 00 00 00 43 6C 6F 73 65 48 61 6E 64 6C 65 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 00 47 65 74 50 72 6F 63 41 64 64 72 65 73 73 00 00 00 45 78 69 74 50 72 6F 63 65 73 73 }

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

• Legacy Application Deployment via Group Policy: When IT admins deploy older, non-updated line-of-business applications (e.g., legacy Java-based tools or old .NET Framework 2.0 apps) to endpoints via Group Policy Software Installation, the installer or the application binary itself may contain PE headers that match the specific encryption pattern or obfuscation signature targeted by EncryptPE2200461622006630WFS.

  • Filter/Exclusion: Exclude files located in standard application directories (e.g., C:\Program Files\, C:\Program Files (x86)\) for known legacy software names, or whitelist specific SHA-256 hashes of the deployed legacy binaries.

• Third-Party Antivirus/EDR Self-Update: Many enterprise security suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or Carbon Black) use encrypted or packed PE modules for their sensor updates or communication channels. During the scheduled update cycle, these components are written to disk and may temporarily match the YARA rule’s encryption pattern before being fully unpacked or registered by the agent.

  • Filter/Exclusion: Exclude processes or file paths associated with known security vendor directories (e.g., C:\ProgramData\CrowdStrike\, C:\Program Files\Microsoft Defender\) and correlate with the parent process being a known security service (e.g., FalconSensor.exe, MsMpEng.exe).

• Scheduled Backup or Archiving Jobs: Enterprise backup solutions (e.g., Veeam, Commvault, or Acronis) often create encrypted or compressed archive files (which may be PE-structured containers or use PE-based encryption wrappers) during nightly scheduled tasks. If the YARA rule scans file content rather than just extension, these encrypted backup chunks can trigger the detection.

  • *Filter/