EXEStealthv11

Hunt Hypothesis

This rule detects the presence of the EXEStealth malware family, a lightweight executable often used for initial access or persistence that may evade standard signature-based detections. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify compromised endpoints early, particularly in environments where traditional EDR coverage may be limited or where low-severity threats are overlooked.

YARA Rule

rule EXEStealthv11
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 00 00 00 00 5D 81 ED FB 1D 40 00 B9 7B 09 00 00 8B F7 AC }

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

• Scenario: Execution of the EXEStealth utility by a DevOps team during a scheduled Windows Server maintenance window to perform silent application patching or log rotation.
  • Filter/Exclusion: Exclude executions where the parent process is Task Scheduler (taskschd.msc or svchost.exe with specific service arguments) AND the file path matches C:\Program Files\InternalTools\EXEStealth\*.exe.
• Scenario: A Security Engineer manually running EXEStealth from a jump host or management workstation to test detection coverage or perform emergency cleanup of rogue processes.
  • Filter/Exclusion: Exclude executions originating from known administrative accounts (e.g., DOMAIN\svc_security_admin) or from specific management subnets (e.g., 10.20.50.0/24) where the user context is an interactive admin session.
• Scenario: An automated CI/CD pipeline agent (e.g., Jenkins or Azure DevOps) invoking EXEStealth as part of a post-build cleanup script to remove temporary build artifacts or kill orphaned service processes.
  • Filter/Exclusion: Exclude executions where the parent process is a known CI/CD agent binary (e.g., java.exe, node.exe, or msbuild.exe) AND the working directory is within the build agent workspace (e.g., C:\agent\_work\).
• Scenario: A third-party backup solution (e.g., Veeam or Commvault) using EXEStealth as a helper utility to temporarily pause or hide specific application processes during the backup snapshot phase.
  • Filter/Exclusion: Exclude executions where the parent process is a known backup agent (e.g., VeeamBackup.exe or commagent.exe) AND the execution