EmbedPE113cyclotron

Hunt Hypothesis

This rule identifies potentially malicious or obfuscated PE executables by detecting specific embedded patterns associated with the “cyclotron” signature, which may indicate the presence of custom loaders or stealthy payloads. Proactively hunting for these artifacts in Azure Sentinel allows the SOC team to uncover low-severity anomalies that could serve as initial access vectors or persistence mechanisms before they escalate into more significant threats.

YARA Rule

rule EmbedPE113cyclotron
{
      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 B8 5E 2D C6 DA FD 48 63 05 3C 71 B8 5E 97 7C 36 7E 32 7C 08 4F 06 51 64 10 A3 F1 4E CF 25 CB 80 D2 99 54 46 ED E1 D3 46 86 2D 10 68 93 83 5C 46 4D 43 9B 8C D6 7C BB 99 69 97 71 2A 2F A3 38 6B 33 }

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

• Scenario: Development teams using Visual Studio or JetBrains Rider to compile C++ projects that include static libraries or embedded resources (such as version info or icons) which match the specific byte patterns of the EmbedPE113cyclotron signature.
  • Filter/Exclusion: Exclude processes originating from known IDE executables (e.g., devenv.exe, idea64.exe, rider64.exe) and their child compilation processes (link.exe, c1.exe) when the file path resides in standard development directories (e.g., C:\Users\*\source\, C:\dev\).
• Scenario: IT administrators running 7-Zip or WinRAR to extract or create archives containing .dll or .exe files that have been patched or built with specific embedding tools (like Enigma Virtual Box or UPX with specific settings) during software distribution or patch management.
  • Filter/Exclusion: Exclude processes named 7z.exe, WinRAR.exe, or unrar.exe when the target file path is within shared network drives (e.g., \\fileserver\software\, \\patchserver\) or local staging folders (C:\staging\, C:\temp\).
• Scenario: Scheduled maintenance jobs using PowerShell or batch scripts to copy or move application binaries (e.g., app.exe) from a build server to production servers, where the binary was previously processed by a custom embedding script (e.g., embed_pe.py or a custom C# tool) to add metadata.
  • Filter/Exclusion: Exclude file operations (CreateFile, CopyFile) where the source or destination path contains keywords like build, dist, release, or artifacts, and the process