ARMProtectorv02SMoKE

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging the ARMProtectorv02SMoKE signature to identify specific malicious artifacts within Azure Sentinel’s workload environment. Proactive hunting for this indicator is essential to uncover early-stage threats that may evade standard detection thresholds due to their low severity classification, ensuring comprehensive visibility into potential compromise vectors.

YARA Rule

rule ARMProtectorv02SMoKE
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 04 00 00 00 83 60 EB 0C 5D EB 05 45 55 EB 04 B8 EB F9 00 C3 E8 00 00 00 00 5D EB 01 00 81 ED 09 20 40 00 EB 02 83 09 8D B5 9A 20 40 00 EB 02 83 09 BA 0B 12 00 00 EB 01 00 8D 8D A5 32 40 00 }

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 ARMProtectorv02SMoKE detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Defender Antivirus Real-Time Protection Scanning

  • Context: The YARA rule may flag the MsMpEng.exe process when it scans large files or updates its signature database. In an enterprise environment with high file I/O, this can trigger frequent alerts as the engine processes executable binaries that match the “SMoKE” heuristic patterns.
  • Suggested Filter/Exclusion: Create a rule exclusion for the specific process path C:\Program Files\Windows Defender\MsMpEng.exe and exclude any events where the parent process is MsMpEng.exe. Additionally, filter out alerts occurring during the scheduled “Antivirus Scan” maintenance window (e.g., 02:00–04:00 UTC).

• Scenario: SCCM/Intune Application Deployment Executables

  • Context: During mass software deployments using Microsoft Endpoint Configuration Manager (SCCM) or Intune, the deployment agent (ccmsetup.exe or Microsoft.IntuneManagementAgent) often extracts temporary installers. These extracted binaries frequently contain ARM-specific headers or obfuscation techniques that mimic the rule’s detection logic for suspicious ARM-based payloads.
  • Suggested Filter/Exclusion: Exclude alerts where the parent process is ccmsetup.exe (SCCM) or Microsoft.IntuneManagementAgent.exe. Implement a filter to suppress alerts generated by processes running within the C:\Windows\CCM\ directory tree, as this path is dedicated to legitimate management traffic.

• Scenario: Scheduled Backup Jobs Using Veeam or Commvault

  • Context: Enterprise backup solutions like Veeam Agent for Windows or Commvault often utilize ARM-optimized compression