Armadillov3xx

Hunt Hypothesis

This detection identifies the presence of Armadillo v3xx malware signatures within the environment to uncover potential fileless or memory-resident threats that may evade traditional signature-based defenses. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to validate false positives and assess lateral movement risks before low-severity detections escalate into active incidents.

YARA Rule

rule Armadillov3xx
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 [4] 5D 50 51 EB 0F B9 EB 0F B8 EB 07 B9 EB 0F 90 EB 08 FD EB 0B F2 EB F5 EB F6 F2 EB 08 FD EB E9 F3 EB E4 FC E9 59 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

Here are 4 specific false positive scenarios for the Armadillov3xx detection rule, including targeted filters and exclusions suitable for an enterprise environment:

• Scenario: Automated Backup Scans by Veeam or Commvault

  • Context: Enterprise backup agents (e.g., Veeam Backup & Replication, Commvault) often utilize the Armadillo encryption engine to secure data streams during scheduled nightly backups. The YARA rule may trigger when these agents spawn child processes that load the Armadillov3xx library into memory while encrypting large file sets.
  • Filter/Exclusion: Create a process exclusion for known backup service executables (e.g., VeeamService.exe, commvault_agent.exe) and their specific child processes running under the system or dedicated backup user account (svc_backup). Exclude alerts where the parent process is one of these trusted services.

• Scenario: Microsoft Defender Antivirus Real-Time Scanning

  • Context: In environments using Microsoft Defender for Endpoint, the real-time protection engine frequently loads various cryptographic modules to scan files in transit. The Armadillo library is often embedded within the MsMpEng.exe process tree when handling encrypted archives or specific EDR telemetry data, causing a match on the YARA signature without malicious intent.
  • Filter/Exclusion: Configure an exclusion based on the parent process name MsMpEng.exe. Additionally, filter out detections where the file path resides within the Microsoft Defender installation directory (e.g., C:\Program Files\Microsoft Defender Antivirus\) or the Windows System32 folder.

• Scenario: Scheduled Group Policy Encryption Tasks

  • Context: Administrative tasks involving BitLocker management or Group Policy Object (GPO) updates often invoke scripts that utilize Armadillo for on-the-fly encryption of configuration files. A scheduled task