ExeShieldvxx

Hunt Hypothesis

This rule identifies executable files protected by the ExeShield packer, a technique often employed by adversaries to obscure code logic and evade static analysis during initial access or payload execution. Proactively hunting for these packed binaries in Azure Sentinel allows the SOC to surface potentially malicious or obfuscated artifacts that may have slipped past standard signature-based detections, ensuring early visibility into stealthy threat activity.

YARA Rule

rule ExeShieldvxx
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 65 78 65 73 68 6C 2E 64 6C 6C C0 5D 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: Deployment of Microsoft Defender for Endpoint or third-party EDR agents (e.g., CrowdStrike Falcon, Carbon Black) that utilize in-memory protection or specific binary signatures to hook into process execution.
  • Filter/Exclusion: Exclude processes where the parent executable is MsMpEng.exe (Defender), FalconSensor.exe (CrowdStrike), or CbService.exe (Carbon Black), or exclude files located in the vendor-specific installation directories (e.g., C:\Program Files\Microsoft Security Client\, C:\ProgramData\CrowdStrike\).
• Scenario: Execution of legitimate software installers or updaters from major vendors (e.g., Adobe Creative Cloud, JetBrains Toolbox, or Visual Studio Installer) that spawn temporary helper executables or self-extracting archives to apply patches.
  • Filter/Exclusion: Exclude processes where the parent process belongs to known vendor installers (e.g., AdobeUpdate.exe, jbinst.exe, setup.exe from C:\Program Files (x86)\Microsoft Visual Studio\Installer\) or where the file path contains vendor-specific subdirectories like \Adobe\, \JetBrains\, or \Microsoft Visual Studio\.
• Scenario: Scheduled maintenance tasks or service management tools (e.g., sc.exe, net1.exe, or custom PowerShell scripts) that restart or update critical system services, potentially triggering signature matches if the service binary is temporarily loaded or replaced.
  • Filter/Exclusion: Exclude processes where the parent is svchost.exe (specifically those hosting known service groups), services.exe, or PowerShell.exe running from C:\Windows\System32\WindowsPowerShell\v1.0\, and where the target file is located in C:\Windows\System32\ or `C:\Windows\Sys