EXELOCK 666 15

Hunt Hypothesis

This hypothesis targets the execution of malicious or suspicious executable files identified by the EXELOCK_666_15 YARA signature, which may indicate the presence of specific malware strains or trojanized binaries. Proactively hunting for this pattern in Azure Sentinel allows the SOC to detect low-severity threats that might evade standard behavioral detections, ensuring early identification of potential footholds before they escalate into more significant incidents.

YARA Rule

rule EXELOCK_666_15: PEiD
{
    strings:
        $a = { BA ?? ?? BF ?? ?? EB ?? EA ?? ?? ?? ?? 79 ?? 7F ?? 7E ?? 1C ?? 48 78 ?? E3 ?? 45 14 ?? 5A E9 }
    condition:
        $a 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

• Scenario: Execution of the 7z.exe or WinRAR.exe archive utility by a DevOps engineer or IT support staff to extract application binaries or configuration files during a deployment or troubleshooting session.
  • Filter/Exclusion: Exclude processes where the parent process is explorer.exe, cmd.exe, or powershell.exe AND the file path matches C:\Program Files\7-Zip\7z.exe or C:\Program Files\WinRAR\WinRAR.exe.
• Scenario: Execution of python.exe or pythonw.exe by a data scientist or application developer running a local script to process logs, generate reports, or test API integrations on a workstation.
  • Filter/Exclusion: Exclude processes where the command line contains arguments like script.py, main.py, or test_*.py AND the user belongs to the DevTeam or DataScience security group.
• Scenario: Execution of node.exe or npm.exe by a frontend developer or build agent running npm install or node build.js as part of a continuous integration/continuous deployment (CI/CD) pipeline or local development workflow.
  • Filter/Exclusion: Exclude processes where the parent process is cmd.exe, powershell.exe, or git.exe AND the file path matches C:\Program Files\nodejs\node.exe or C:\Users\<User>\AppData\Roaming\npm\node_modules\....
• Scenario: Execution of java.exe or javaw.exe by an application server or middleware service (e.g., Tomcat, JBoss, or a custom Java-based microservice) starting up or restarting during a scheduled maintenance window.
  • Filter/Exclusion: Exclude processes where the parent process is