Armadillov275a

Hunt Hypothesis

This rule identifies the presence of Armadillo malware, a known threat actor tool often used for initial access or lateral movement, by matching specific file signatures within the environment. Proactively hunting for this signature allows the SOC to detect dormant or low-noise infections that may evade standard behavioral detections, ensuring early identification of compromised assets before they are leveraged for deeper network penetration.

YARA Rule

rule Armadillov275a
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 68 [3] 68 D0 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 28 [3] 33 D2 8A D4 89 15 24 }

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 sysadmin uses 7-Zip or WinRAR to extract a large software bundle or log archive on a workstation. The YARA rule likely targets specific byte patterns or entropy levels common in compressed archives, causing the executable or the extracted files to match the signature.

  • Filter/Exclusion: Exclude processes named 7z.exe, 7zG.exe, WinRAR.exe, or WinRAR.exe from the detection scope, or filter out file paths ending in common archive extensions (.zip, .rar, .7z) if the rule is file-based.

• Scenario: An IT administrator runs VirusTotal Uploader or a similar internal scanning tool to check a new binary before deployment. The tool may temporarily write the file to a temp directory or load it into memory, triggering the YARA scan on the file or process.

  • Filter/Exclusion: Exclude the specific executable names of known scanning utilities (e.g., vtuploader.exe, clamscan.exe, mbsa.exe) or exclude file paths containing \Temp\ or \AppData\Local\Temp\ if the rule is not designed to catch temp file execution.

• Scenario: A scheduled task runs PowerShell to execute a maintenance script that loads a custom .NET assembly or native DLL. If the YARA rule targets specific code patterns or string constants found in common utility libraries (e.g., Microsoft.VisualBasic.dll or custom internal libraries), it may flag the loaded module.

  • Filter/Exclusion: Exclude known legitimate .NET assemblies or specific DLL names (e.g., System.Core.dll, System.Data.dll) from the file-based YARA scan, or add a process filter for powershell.exe and pwsh.exe if the rule is process-based and the match is due to loaded