Armadillov220b1

Hunt Hypothesis

This YARA rule targets the Armadillo malware family, a known threat actor associated with the APT28 (Cozy Bear) group, by identifying specific code patterns or strings indicative of its presence in memory or on disk. Proactively hunting for this signature allows the SOC to detect early-stage espionage or reconnaissance activities before the adversary establishes persistence or executes further post-exploitation actions within the Azure environment.

YARA Rule

rule Armadillov220b1
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 30 12 41 00 68 A4 A5 40 00 64 A1 00 00 00 00 50 64 89 25 00 00 00 00 83 EC 58 }

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: A developer or CI/CD pipeline agent executes a custom build script or utility named armadillo (or containing that string) to compile C/C++ code or process data, where the binary or script header matches the YARA signature due to embedded metadata or specific byte patterns.
  • Filter/Exclusion: Exclude processes where the parent process is a known build tool (e.g., msbuild.exe, dotnet.exe, python.exe) or where the process path resides in standard development directories (e.g., C:\dev\, C:\builds\, C:\src\).
• Scenario: An IT administrator deploys a custom internal tool or agent for network monitoring or asset inventory that is internally branded or named with the “Armadillo” prefix (e.g., ArmadilloAgent.exe, armadillo_scan.dll) for versioning or project codename purposes, triggering the rule on every host where the agent is installed.
  • Filter/Exclusion: Exclude processes where the executable name is exactly ArmadilloAgent.exe or armadillo_scan.dll and the path is within the standard installation directory (e.g., C:\Program Files\InternalTools\Armadillo\).
• Scenario: A security team runs a manual threat hunt or memory dump analysis using a tool that includes the YARA rule Armadillov220b1 in its scan set, causing the rule to match against the tool’s own configuration file, script, or embedded YARA database file during the scan process.
  • Filter/Exclusion: Exclude file paths that end with .yar, .yara, or .rules and are located in security tool directories (e.g., C:\Tools\YARA\, C:\Security\ThreatHunt\).