tElockv051

Hunt Hypothesis

This detection identifies potential file-based threats matching the specific signature defined by the YARA rule tElockv051, which may indicate early-stage malware or suspicious artifacts within the environment. Proactively hunting for this signal in Azure Sentinel allows the SOC team to validate low-severity alerts against broader context and prevent minor anomalies from evolving into significant incidents before they impact critical assets.

YARA Rule

rule tElockv051
{
      meta:
		author="malware-lu"
strings:
		$a0 = { C1 EE 00 66 8B C9 EB 01 EB 60 EB 01 EB 9C E8 00 00 00 00 5E 83 C6 5E 8B FE 68 79 01 59 EB 01 EB AC 54 E8 03 5C EB 08 }

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 tElockv051 detection rule, tailored for an enterprise environment:

• Scenario: Microsoft Defender Antivirus (or similar EDR) performing real-time scanning on a large database file in use by SQL Server.

  • Context: The YARA signature likely flags specific byte patterns or PE headers associated with the antivirus engine’s scanning process, which can mimic malicious behavior when locking files.
  • Filter/Exclusion: Add an exclusion for the MsMpEng.exe (Microsoft Defender) and sqlservr.exe processes within the detection logic to ignore events where the parent process is one of these services.

• Scenario: Scheduled nightly backup jobs executed by Veeam Backup & Replication or Commvault.

  • Context: During the “lock” phase of a full backup, the agent creates temporary lock files and modifies metadata in shared network folders, triggering the rule’s file-locking logic.
  • Filter/Exclusion: Create a time-based exclusion window (e.g., 01:00–05:00 local time) for hosts tagged with “Backup Server” or filter out events where the executable path contains \Veeam\ or \Commvault\.

• Scenario: Deployment of patches via SCCM (System Center Configuration Manager) or Intune Management Extension.

  • Context: When the ccmsetup.exe or IntuneManagementExtension.exe applies updates, it often locks system DLLs and registry keys to prevent conflicts during installation, which matches the rule’s detection criteria for unauthorized locking mechanisms.
  • Filter/Exclusion: Exclude events where the command line arguments contain keywords like /install, /update, or specific SCCM deployment IDs (e.g., CCMDeploymentID).

• **Scenario