EncryptPE22006710220061025WFS

Hunt Hypothesis

This detection identifies potential fileless or packed malware activity by leveraging a specific YARA signature to scan for encrypted Portable Executable (PE) structures often used by adversaries to obfuscate malicious payloads. The SOC team should proactively hunt for this behavior in Azure Sentinel because low-severity alerts regarding encrypted binaries can indicate early-stage lateral movement or command-and-control communication that may escalate into critical incidents if not investigated immediately.

YARA Rule

rule EncryptPE22006710220061025WFS
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 9C 64 FF 35 00 00 00 00 E8 73 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 54 65 6D 70 50 61 74 68 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

Here are 4 specific false positive scenarios for the EncryptPE22006710220061025WFS detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Defender Antivirus (MDE) Real-Time Scanning

  • Context: The MDE engine frequently scans executable files in real-time. When it encounters a PE file that has been recently modified or downloaded by the user, its internal encryption module may trigger this specific YARA signature while processing the file header.
  • Suggested Filter/Exclusion: Create an exclusion for the process MsMpEng.exe (Microsoft Defender Antivirus) on the endpoint level. Additionally, add a rule filter to exclude alerts where the parent process is MsMpEng.exe and the file path resides within the standard Windows installation directory (C:\Program Files\Windows Defender\).

• Scenario: Scheduled Backup Jobs via Veeam or Commvault

  • Context: Enterprise backup agents (e.g., Veeam Agent, Commvault Command Center) regularly encrypt and package PE files during scheduled maintenance windows. The YARA rule may detect the encryption headers generated by these agents as suspicious activity when they process large batches of executables in the C:\ProgramData or user document folders.
  • Suggested Filter/Exclusion: Implement a time-based exclusion for alerts occurring between 02:00 and 06:00 UTC on weekdays, specifically targeting processes named VeeamAgent.exe, CommServe.exe, or BackupEngine.exe. Alternatively, exclude file paths containing \Veeam\ or \Commvault\.

• Scenario: Software Deployment via Microsoft Endpoint Configuration Manager (MECM/SCCM)

  • Context: During application deployment cycles, SCCM pushes encrypted installation packages to endpoints. The