ACProtectv135riscosoftwareIncAnticrackSoftware

Hunt Hypothesis

This rule detects the presence of ACProtect v1.35, a commercial software protection tool often used by adversaries to pack executables and obscure their code from static analysis. Proactively hunting for this specific version helps identify potentially obfuscated malware or trojans that may be leveraging commercial packers to evade standard signature-based detections within the Azure Sentinel environment.

YARA Rule

rule ACProtectv135riscosoftwareIncAnticrackSoftware
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 4B 45 52 4E 45 4C 33 32 2E 44 4C 4C 00 [20] 55 53 45 52 33 32 2E 44 4C 4C 00 [33] 00 47 65 74 50 72 6F 63 }

condition:
		$a0
}

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 QA engineer manually runs a legacy application protected by ACProtect v1.35 (e.g., LegacyBillingApp.exe) from a local network share or USB drive to verify a hotfix, rather than executing it from the standard installed directory.

  • Filter/Exclusion: Exclude file paths where the parent directory contains \\Share\QA\ or \\Share\Dev\, or specifically exclude the known binary name LegacyBillingApp.exe if it is not running from C:\Program Files\.

• Scenario: An IT administrator uses a portable version of a utility tool (e.g., Sysinternals\ProcessMonitor.exe or a custom internal script DBBackupUtility.exe) that has been packed with ACProtect to reduce file size or protect IP, and copies it to a temporary folder (C:\Temp\ or %USERPROFILE%\Downloads\) for quick execution.

  • Filter/Exclusion: Exclude processes where the command line arguments indicate a backup or maintenance task (e.g., *backup*, *maintain*), or exclude execution from C:\Temp\ and C:\Users\*\Downloads\ if the parent process is a known admin tool like cmd.exe or powershell.exe initiated by an admin account.

• Scenario: A scheduled task or service starts a protected installer or updater (e.g., VendorAppUpdater.exe protected by ACProtect) that is located in a non-standard directory like C:\VendorApps\Updates\ instead of the typical C:\Program Files\VendorApp\.

  • Filter/Exclusion: Exclude file paths matching C:\VendorApps\ or C:\Updates\, or whitelist specific known vendor updater executables (e.g., VendorAppUpdater.exe) regardless of their location, provided they