UnknownbySMT

Hunt Hypothesis

This detection identifies files flagged by an unknown SMT signature pattern that may indicate novel malware or unclassified software attempting to operate within the environment. Proactive hunting for these anomalies in Azure Sentinel is essential to validate false positives and uncover emerging threats before they escalate into confirmed incidents, ensuring comprehensive coverage against evolving attack vectors.

YARA Rule

rule UnknownbySMT
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 BE [4] 8D BE [4] 83 [2] 57 EB }

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 5 specific false positive scenarios for the UnknownbySMT detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Automated Patch Deployment via SCCM/Intune

  • Context: The System Center Configuration Manager (SCCM) or Microsoft Intune agent executes a scheduled patch installation task. This process often spawns temporary executables with varying hashes that have not yet been ingested into the global reputation database, triggering an “Unknown” status upon their first run on specific endpoints.
  • Filter/Exclusion: Create a whitelist exclusion based on the parent process path C:\Windows\CCM\PolicyAgent.exe or C:\Program Files (x86)\Microsoft Intune Management Extension\IntuneManagementExtension.exe. Additionally, filter out events where the file age is greater than 24 hours to ignore newly deployed but known agents.

• Scenario: Third-Party Backup Agent Scanning

  • Context: Enterprise backup solutions like Veeam Backup & Replication or Commvault run scheduled jobs that extract and verify data integrity using proprietary helper binaries. These binaries often generate unique hashes per tenant or job instance, appearing as “Unknown” to the YARA rule despite being trusted components of the backup infrastructure.
  • Filter/Exclusion: Exclude file paths matching C:\Program Files\Veeam\Backup and Replication\ and C:\Program Files\Commvault\. Apply a filter where the process command line contains keywords like “VeeamAgent.exe” or “cvbdagent” to bypass detection for these specific backup processes.

• Scenario: Development Build Execution in CI/CD Pipelines

  • Context: In DevOps environments, Jenkins or Azure Dev Agents execute build pipelines that compile code and run unit tests. These agents frequently download and execute temporary artifacts (e.g.,