Armadillov190b3

Hunt Hypothesis

This hypothesis targets the presence of the Armadillo malware variant, a known threat actor tool that often establishes persistence or executes malicious payloads within Azure environments. Proactively hunting for this specific YARA signature allows the SOC team to identify low-severity infections early, preventing potential lateral movement or data exfiltration before they escalate in severity.

YARA Rule

rule Armadillov190b3
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 08 E2 40 00 68 94 95 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 DevOps engineer runs a local build pipeline using Jenkins or GitHub Actions that compiles C/C++ code into a shared library (.dll or .so). The resulting binary contains specific string patterns or section headers that match the YARA signature Armadillov190b3 due to standard compiler output or embedded metadata.

  • Filter/Exclusion: Exclude files located in standard build artifact directories (e.g., C:\builds\, /var/tmp/build/, or *.artifacts\) and exclude processes spawned by build agents like java.exe (Jenkins) or node.exe (GitHub Actions) when the file extension is .dll, .so, or .exe and the parent process is a known build tool.

• Scenario: An IT administrator deploys a new version of Adobe Acrobat Reader or Microsoft Office via SCCM (System Center Configuration Manager) or Intune. The installer or the updated binary contains a version string or resource section that coincidentally matches the YARA rule’s string criteria, particularly if the rule targets specific version numbers or GUIDs embedded in the binary.

  • Filter/Exclusion: Exclude files with names matching known software installers (e.g., setup.exe, msiexec.exe, wusa.exe) and exclude files located in C:\Windows\Installer\ or C:\Program Files\ where the parent process is msiexec.exe or wuaexer.exe.

• Scenario: A security team runs a VirusTotal or ClamAV scan on a large dataset of quarantined files or a backup archive. The scanning engine itself or the temporary files created during the scan process may contain metadata or temporary strings that trigger the rule, especially if the rule is sensitive