EmbedPEV1Xcyclotron

Hunt Hypothesis

This detection identifies potential fileless or memory-resident threats by scanning for specific Cyclotron-embedded patterns within PE executables that may indicate early-stage adversary activity. A proactive hunt is essential in Azure Sentinel to uncover stealthy malware variants that evade traditional signature-based defenses, ensuring rapid identification of low-severity anomalies before they escalate into broader incidents.

YARA Rule

rule EmbedPEV1Xcyclotron
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 83 EC 50 60 68 [4] E8 [2] 00 00 }

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 EmbedPEV1Xcyclotron detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Scheduled Antivirus Definition Updates via Microsoft Endpoint Configuration Manager (MECM/SCCM)

  • Context: The SCCM client service (ccmexec.exe) frequently injects new definition updates or scans embedded PE files into the system memory during nightly maintenance windows, triggering the rule’s signature for embedded payloads.
  • Filter/Exclusion: Create a process exclusion for C:\Program Files\Microsoft Configuration Manager\bin\x64\ccmexec.exe and its child processes when running on the specific service account (e.g., NT SERVICE\CcmExec). Additionally, exclude file paths matching *\Windows\System32\ccm\*.

• Scenario: Automated Patch Deployment by Ivanti Neurons or ManageEngine Endpoint Central

  • Context: During automated patch cycles, the deployment agent extracts embedded installer packages (often containing PE executables) to a temporary staging directory before execution. The YARA rule detects these extracted artifacts as potential malicious embeddings.
  • Filter/Exclusion: Exclude file paths located within standard vendor staging directories, such as C:\Program Files\Ivanti\Neurons\Agent\Staging\* or C:\ManageEngine\EndpointCentral\Temp\*. Apply a filter to ignore events where the parent process is agent.exe (Ivanti) or MECAgentService.exe (ManageEngine).

• Scenario: Office 365 Click-to-Run Update Service Activity

  • Context: The Microsoft Office Click-to-Run service (OfficeClickToRun.exe) periodically downloads and embeds update manifests or component files into the user profile directory. These updates often contain embedded PE structures that match