ACProtectV20risco

Hunt Hypothesis

This rule detects the presence of ACProtect v2.0 packed executables, a common obfuscation technique used by adversaries to hide malicious payloads and evade static analysis. Proactively hunting for these signatures helps identify potentially compromised endpoints or staged malware that may be leveraging packing to bypass initial security controls.

YARA Rule

rule ACProtectV20risco
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 [4] 68 [4] C3 C3 }

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

• Legacy .NET Application Deployment via Group Policy

  • Scenario: Administrators deploy older, custom-built line-of-business applications (e.g., inventory management or legacy POS systems) that were compiled with ACProtect 2.0 to protect intellectual property. These executables are pushed to endpoints via Group Policy Software Installation or SCCM, triggering the YARA rule on the C:\Windows\Installer or application install directories.
  • Filter/Exclusion: Exclude files located in specific application install directories (e.g., C:\Program Files\LegacyApp\) or exclude based on the parent process being gpupdate.exe or ccmsetup.exe during the installation window.

• Third-Party Utility Tools in Admin Shares

  • Scenario: IT support teams place utility tools (such as disk cleanup scripts, password reset utilities, or network diagnostic tools) in administrative shares (e.g., C:\$ADMIN, C:\Tools\) for remote troubleshooting. Some of these niche utilities, particularly those from smaller vendors or older open-source projects, may be packed with ACProtect 2.0 to reduce file size or obfuscate code.
  • Filter/Exclusion: Exclude files residing in known administrative share paths (e.g., \\*\$ADMIN, C:\$ADMIN) or specific tool directories (e.g., C:\Tools\, C:\Admin\Utils\) if the file hash matches a known good list of approved utilities.

• Scheduled Maintenance Jobs for Legacy Services

  • Scenario: A scheduled task runs a legacy maintenance script or executable (e.g., a database log rotation tool or a custom backup agent) that has been packed with ACProtect 2.0. This executable is stored in a service directory (e.g., C:\Program Files\MyService\bin\) and is