EmbedPEV100V124cyclotron

Hunt Hypothesis

This detection identifies potential adversary activity involving embedded PE executables that match specific Cyclotron signatures, indicating possible file-based persistence or initial access mechanisms. A proactive hunt is essential to uncover stealthy threats that may evade standard signature-based defenses by analyzing these embedded artifacts for anomalous behavior within the Azure Sentinel environment.

YARA Rule

rule EmbedPEV100V124cyclotron
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 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 [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 47 65 74 4D 6F 64 75 6C 65 48 61 6E 64 6C 65 41 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 00 00 00 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

Here are 5 specific false positive scenarios for the EmbedPEV100V124cyclotron detection rule, including targeted filters and exclusions:

• Scenario: Microsoft Defender Antivirus Engine Updates

  • Context: The YARA rule detects embedded PE signatures often found in antivirus engine updates. When Microsoft Defender performs its scheduled daily definition update (via the MsMpEng.exe process), it extracts new protection packages that match the Cyclotron heuristic signature, triggering an alert on the updated .cab or .dll files within the ProgramData\Microsoft\Windows Defender directory.
  • Filter/Exclusion: Create a path-based exclusion for C:\ProgramData\Microsoft\Windows Defender\* and exclude process names matching MsMpEng.exe when the file extension is .cab or .dll.

• Scenario: SCCM (MECM) Application Deployment

  • Context: During a scheduled deployment of enterprise applications via Microsoft Endpoint Configuration Manager (SCCM), the client service (CcmExec.exe) extracts application binaries containing embedded PE headers. If the deployed application includes a Cyclotron-based security component or uses a similar embedding structure, the rule triggers on the temporary extraction folder in C:\Windows\CCMCache.
  • Filter/Exclusion: Exclude files located within the C:\Windows\CCMCache directory when the parent process is CcmExec.exe, specifically during business hours (08:00–18:00) to align with standard deployment windows.

• Scenario: Adobe Acrobat Pro Automated Updates

  • Context: The rule may flag the background update service of Adobe Acrobat Pro (AcroRdr64.exe or AdobeARMService). When the application performs a silent update check, it loads embedded PDF rendering libraries that utilize PE structures matching the Cycl