ACProtectV14Xrisco

Hunt Hypothesis

This detection identifies the execution of files protected by ACProtect v14, a common packing technique often leveraged by adversaries to obfuscate malicious payloads and evade static analysis. Proactively hunting for this behavior in Azure Sentinel is essential because low-severity alerts for packed executables frequently mask sophisticated threats that require deeper behavioral investigation to confirm their legitimacy or identify hidden attack chains.

YARA Rule

rule ACProtectV14Xrisco
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 01 00 00 00 7C 83 04 24 06 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

False Positive Scenarios for Rule: ACProtectV14Xrisco

• Scenario 1: Scheduled Antivirus Definition Updates

  • Context: The enterprise uses Microsoft Defender for Endpoint or Symantec Endpoint Protection. During the nightly maintenance window (e.g., 02:00 AM), the AV service automatically downloads and installs new virus definition packages. These updates often involve unpacking compressed archives containing protected executables that match the ACProtect signature logic, triggering a hit on the rule.
  • Suggested Filter: Exclude processes where the parent process is the specific AV updater (e.g., MsMpEng.exe, Symantec Antivirus Console.exe) running under the SYSTEM account during defined maintenance windows.

• Scenario 2: Deployment of Patched Applications via SCCM/Intune

  • Context: The IT operations team utilizes Microsoft Endpoint Configuration Manager (SCCM) or Microsoft Intune to push application patches (e.g., Adobe Acrobat Reader, Microsoft Office updates) to workstations. These installers frequently bundle protected components wrapped in ACProtect shells to prevent tampering. When the deployment agent executes these installers, the rule flags them as potential Xrisco activity.
  • Suggested Filter: Create an exclusion for file paths located within standard software distribution directories (e.g., C:\Windows\CCM\, C:\Program Files\Microsoft Intune Agent\) and whitelist known installer hashes associated with trusted vendors like Adobe or Microsoft.

• Scenario 3: Execution of Legacy Internal Reporting Tools

  • Context: A legacy internal financial reporting tool (e.g., a custom .NET application named “FinReport.exe”) is distributed across the finance department. This application was originally compiled and protected using ACProtect v14 to ensure license integrity. When users or scheduled background services launch