EmbedPEv113cyclotron

Hunt Hypothesis

This detection identifies potential fileless or embedded malware activity by leveraging Cyclone’s YARA signatures to uncover hidden executable structures within PE files that may evade standard AV solutions. Proactively hunting for these indicators in Azure Sentinel is essential to detect early-stage supply chain compromises or lateral movement attempts before they escalate into significant security incidents.

YARA Rule

rule EmbedPEv113cyclotron
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 83 EC 50 60 68 5D B9 52 5A E8 2F 99 00 00 DC 99 F3 57 05 68 }

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 5 specific false positive scenarios for the EmbedPEv113cyclotron detection rule, tailored for an enterprise environment:

• Scenario: Microsoft Office Macro Execution via PowerShell

  • Context: Administrators frequently use PowerShell.exe to automate Excel or Word macro processing (e.g., bulk report generation). The YARA rule may flag the embedded PE resources within the Office executable when it loads complex macros containing Cyclone-specific signatures.
  • Filter/Exclusion: Exclude processes where the parent process is powershell.exe and the command line contains parameters related to Office automation (e.g., -Command "Import-Module Microsoft.PowerShell.Host"). Additionally, add a hash-based exclusion for known good versions of EXCEL.EXE and WINWORD.EXE.

• Scenario: Antivirus Engine Scanning via Endpoint Protection

  • Context: Enterprise endpoint protection suites (such as CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne) often inject their own scanning engines into memory. When these agents scan user documents, the embedded PE structures of the scanner’s helper processes can trigger the Cyclotron signature logic.
  • Filter/Exclusion: Create a whitelist for known security vendor binaries (e.g., C:\Program Files\CrowdStrike\fsquarantine.exe or C:\Windows\System32\MsMpEng.exe). Filter alerts where the process path resides within standard security installation directories (C:\ProgramData, C:\Program Files\Common Files) and the user context is SYSTEM.

• Scenario: Scheduled Backup Jobs using Veeam or Commvault

  • Context: Automated backup agents run nightly scheduled jobs that compress and archive data. These agents often utilize embedded PE libraries to handle encryption and compression streams, which can mimic the signature patterns detected by the rule during