Armadillov261

Hunt Hypothesis

This detection identifies potential malware activity matching the Armadillov261 signature through YARA scanning on endpoint or file artifacts within the Azure Sentinel environment. Proactive hunting for this behavior is essential to uncover early-stage threats that may not trigger high-severity alerts, allowing the SOC team to investigate and contain low-fidelity indicators before they escalate into broader incidents.

YARA Rule

rule Armadillov261
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 28 [3] 68 E4 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 6C [3] 33 D2 8A D4 89 15 0C }

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 5 specific false positive scenarios for the Armadillov261 detection rule in an enterprise environment, including suggested filters and exclusions:

• Scenario: Legitimate execution of Microsoft Defender Antivirus (MSRT) updates during scheduled maintenance windows.

  • Context: The YARA signature may match the behavior or file hash of MpCmdRun.exe when it performs on-demand scans or downloads definition updates, mimicking the Armadillo malware’s process creation patterns.
  • Filter/Exclusion: Exclude processes where the parent executable is C:\Program Files\Windows Defender\MpCmdRun.exe and the file path contains \Platform\. Additionally, add a time-based filter to suppress alerts between 01:00 and 05:00 UTC on weekdays.

• Scenario: Deployment of enterprise applications via Microsoft Endpoint Configuration Manager (SCCM) or Intune.

  • Context: When SCCM pushes software updates or patches, the ccmsetup.exe or WuaHandler.exe processes often spawn child processes that match the Armadillov261 signature logic, particularly when installing .NET components or Java runtimes.
  • Filter/Exclusion: Create a whitelist for process names ccmsetup.exe, WUAHandler.exe, and msiexec.exe where the command line contains arguments like /quiet, /norestart, or specific SCCM deployment IDs (e.g., -DeploymentID).

• Scenario: Execution of third-party backup agents such as Veeam Backup & Replication or Rubrik.

  • Context: The rule may trigger when the Veeam Agent (vbr.exe) or Rubrik agent initiates a scheduled backup job, as these tools frequently utilize similar memory injection techniques or file I/O patterns that overlap with Arm