Armadillov251

Hunt Hypothesis

This detection identifies potential malicious activity associated with the Armadillo malware family by leveraging a specific YARA signature to scan for known code patterns within the environment. Proactive hunting is essential in Azure Sentinel to uncover early-stage infections that may evade standard signature-based defenses, allowing the SOC team to isolate affected assets before lateral movement occurs.

YARA Rule

rule Armadillov251
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 B8 [3] 68 D0 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 20 }

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 3-5 specific false positive scenarios for the Armadillov251 detection rule in an enterprise environment, including suggested filters and exclusions:

• Scenario: Automated Patch Deployment via SCCM/Intune

  • Context: During scheduled maintenance windows, System Center Configuration Manager (SCCM) or Microsoft Intune pushes updates to endpoints. The deployment agent often executes a temporary binary that mimics the behavior of the Armadillo threat family by injecting code into system processes to apply patches silently.
  • Filter/Exclusion: Create an exclusion based on the specific file path and publisher signature.
    • Condition: File.Path contains "C:\Windows\CCM\ AND Publisher.Name equals "Microsoft Corporation"
    • Action: Exclude events where the parent process is ccmsetup.exe or IntuneManagementExtension.exe.

• Scenario: Endpoint Protection Engine Scans (CrowdStrike/SentinelOne)

  • Context: The enterprise’s primary EDR solution (e.g., CrowdStrike Falcon or SentinelOne) performs a deep heuristic scan. During the scan, the EDR agent spawns child processes that utilize memory injection techniques similar to Armadillov251 to analyze running applications without disrupting user workflows.
  • Filter/Exclusion: Filter out events originating from known EDR service accounts and specific process names.
    • Condition: Process.Name IN ("CcmService.exe", "SentinelOneAgent.exe") AND User.Context equals "SYSTEM"
    • Action: Exclude detections where the parent process is a recognized security agent running under the SYSTEM account during non-business hours (e.g., 02:00–05:00).

• Scenario: Backup and Archiving Operations (Veeam/Acronis) *