ExeShieldv27

Hunt Hypothesis

This rule detects the presence of executables packed or protected by the ExeShield v27 tool, a technique often employed by adversaries to obfuscate malicious binaries and evade static analysis. Proactively hunting for these artifacts in Azure Sentinel allows the SOC to identify potentially hidden payloads or compromised hosts before they execute further post-exploitation actions.

YARA Rule

rule ExeShieldv27
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB 06 68 F4 86 06 00 C3 9C 60 E8 02 00 00 }

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: A developer or sysadmin manually compiles a custom C/C++ utility using gcc or clang on a build server or developer workstation, where the resulting binary retains specific debug symbols or string patterns that match the ExeShieldv27 signature.
  • Filter/Exclusion: Exclude alerts where the parent process is gcc.exe, clang.exe, or msbuild.exe, and the file path resides in a known build directory (e.g., C:\build\, C:\src\) or is owned by a user account in the DevTeam security group.
• Scenario: An enterprise application installer (e.g., setup.exe for Adobe Creative Cloud, Oracle Java, or Microsoft Office) extracts a temporary executable to %TEMP% or %LOCALAPPDATA% to perform a quick integrity check or patch application, triggering the rule due to the binary’s specific header or string content.
  • Filter/Exclusion: Exclude alerts where the parent process is a known installer executable (e.g., setup.exe, install.exe, uninstall.exe) and the file path contains Temp, Local, or Install directories, provided the parent process hash is in the approved installer whitelist.
• Scenario: A scheduled task runs a proprietary internal tool (e.g., logrotator.exe or backup_agent.exe) that is digitally signed by the organization’s internal CA but has a specific version string or resource entry that matches the YARA pattern, often occurring during off-hours maintenance windows.
  • Filter/Exclusion: Exclude alerts where the file is digitally signed by the internal organization name (e.g., “Contoso Corp”) and the parent process is svchost.exe (for service-based tasks) or Task Scheduler (taskschd.msi), and the file path matches