Armadillov252

Hunt Hypothesis

This detection identifies the presence of the Armadillo malware family on endpoints by leveraging a specific YARA signature to capture known malicious artifacts within the Azure Sentinel environment. Proactive hunting for this indicator is essential to uncover early-stage infections that may exhibit low severity initially but could evolve into significant threats if left unaddressed before lateral movement occurs.

YARA Rule

rule Armadillov252
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 [4] E0 [4] 68 D4 64 A1 00 00 00 00 50 64 89 25 00 00 00 00 83 EC 58 53 56 57 89 65 E8 FF [3] 15 38 }
	$a1 = { 55 8B EC 6A FF 68 E0 [3] 68 D4 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 38 }

condition:
		$a0 at pe.entry_point or $a1 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 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 3-5 specific false positive scenarios for the Armadillov252 detection rule, tailored for a legitimate enterprise environment:

• Scenario: Automated Patch Deployment via Microsoft Endpoint Configuration Manager (SCCM)

  • Context: The SCCM client service (ccmexec.exe) frequently executes background tasks to download and install security updates or application patches. These processes often spawn child processes that match the Armadillo signature due to their behavior of reading/writing specific registry keys and network socket creation during deployment windows (e.g., 02:00 AM daily).
  • Suggested Filter/Exclusion: Create a process exclusion for ccmexec.exe when the parent process is wuauserv.exe or taskeng.exe, specifically limiting the scope to the “System” user context during maintenance windows.

• Scenario: Scheduled Antivirus Definition Updates by CrowdStrike Falcon

  • Context: The CrowdStrike Falcon sensor (csfalcon.exe) runs a scheduled job every 4 hours to fetch new definition signatures from the cloud. This activity involves high I/O operations and temporary file creation in the C:\ProgramData\CrowdStrike directory, which often triggers the Armadillov252 logic regarding file system manipulation patterns.
  • Suggested Filter/Exclusion: Add a path-based exclusion for any process originating from C:\Program Files\CrowdStrike\ or C:\ProgramData\CrowdStrike\, ensuring that definition update tasks do not generate alerts regardless of the specific child process name.

• Scenario: Enterprise Backup Operations via Veeam Backup & Replication

  • Context: During nightly backup windows, the Veeam transport service (VeeamTransportService.exe) performs intensive data compression and encryption operations on virtual machine snapshots. The rule detects these high-volume file