tElockv090

Hunt Hypothesis

This detection identifies potential malware or suspicious artifacts matching the specific signature defined by the YARA rule tElockv090 within Azure Sentinel’s telemetry. Proactive hunting for this indicator is essential to uncover stealthy threats that may evade standard high-severity alerts, allowing the SOC team to validate low-fidelity signals before they escalate into broader incidents.

YARA Rule

rule tElockv090
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 02 00 00 00 E8 00 E8 00 00 00 00 5E 2B }

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 tElockv090 detection rule in an enterprise environment, along with recommended filters and exclusions:

• Scenario: Microsoft Defender Antivirus (MSRT) Scheduled Scans

  • Context: The daily scheduled scan initiated by MsMpEng.exe often triggers the rule when it scans large archives or compresses logs in temporary directories.
  • Filter/Exclusion: Add a process exclusion for C:\Program Files\Windows Defender\MsMpEng.exe and exclude the specific file path pattern C:\ProgramData\Microsoft\Windows Defender\Scans\*.

• Scenario: Sysmon Event Collection by Elastic Agent

  • Context: The Elastic Agent (running as elastic-agent.exe) frequently performs real-time log ingestion and compression of audit logs, which mimics the behavior detected by tElockv090.
  • Filter/Exclusion: Create a rule exclusion based on the process name elastic-agent.exe and restrict the detection scope to exclude paths under C:\Program Files\Elastic\Agent\data\.

• Scenario: Backup Operations via Veeam Backup & Replication

  • Context: During nightly backup windows, the Veeam service (Veeam.Backup.Service.exe) creates temporary lock files and archives on the file system to ensure data consistency during replication.
  • Filter/Exclusion: Exclude the process Veeam.Backup.Service.exe from detection and whitelist the directory tree C:\ProgramData\Veeam\Backup\*.

• Scenario: Adobe Acrobat Pro Document Processing

  • Context: When users or automated workflows convert PDFs using Adobe Acrobat (AcroRdrDC.exe), the application generates temporary lock files to manage file access during