Armadillov253

Hunt Hypothesis

This detection identifies the execution of files matching the Armadillov253 YARA signature, which may indicate the presence of a specific malware variant or benign software requiring validation. Proactive hunting for this indicator in Azure Sentinel is essential to distinguish between legitimate applications and potential low-severity threats that could serve as early indicators of broader compromise within the environment.

YARA Rule

rule Armadillov253
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 40 [3] 68 54 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 58 [3] 33 D2 8A D4 89 15 EC }
	$a1 = { 55 8B EC 6A FF 68 [4] 40 [4] 68 54 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 58 33 D2 8A D4 89 }

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 4 specific false positive scenarios for the Armadillov253 detection rule, including targeted filters and exclusions:

• Scenario: Legitimate execution of the Microsoft Defender Antivirus (or Windows Defender) scanning engine (MsMpEng.exe) performing a scheduled scan or on-access monitoring. The YARA signature may match specific heuristic patterns within the antivirus payload that resemble Armadillo behavior.

  • Suggested Filter/Exclusion: Exclude processes where ParentImage is C:\Program Files\Windows Defender\MsMpEng.exe and the process name matches MsMpEng.exe. Alternatively, add a signature exclusion in the EDR console for the specific YARA rule ID when the parent process is a known security vendor.

• Scenario: Automated deployment of updates via Microsoft System Center Configuration Manager (SCCM) or Endpoint Configuration Manager. During package installation, the ccmsetup.exe or wuauserv service may spawn child processes that load scripts matching the Armadillov253 signature logic.

  • Suggested Filter/Exclusion: Create a rule exclusion based on ProcessName containing ccmsetup, WUAHandler, or TaskHost.exe where the CommandLine contains keywords like “SoftwareUpdate” or “PatchDeployment”.

• Scenario: Execution of enterprise backup agents, specifically Veeam Backup & Replication (vbrservice.exe) or Rubrik, which utilize similar memory structures and file I/O patterns during their nightly backup windows. The YARA rule might flag the agent’s internal compression or encryption modules as suspicious Armadillo activity.

  • Suggested Filter/Exclusion: Exclude alerts where ProcessName matches vbrservice.exe, rubrik-agent.exe, or backupengine.exe and the execution time falls within a defined maintenance window