ASProtect v123 RC1

Hunt Hypothesis

This rule identifies the presence of ASProtect v123 RC1, a commercial packer frequently abused by threat actors to obfuscate malicious payloads and evade static analysis. Proactively hunting for this signature allows the SOC to uncover hidden malware or trojans that may have been deployed on endpoints, ensuring early detection of stealthy threats that rely on packing techniques to bypass initial security controls.

YARA Rule

rule ASProtect_v123_RC1: PEiD
{
    strings:
        $a = { 68 01 ?? ?? 00 E8 01 00 00 00 C3 C3 }
    condition:
        $a 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 Application Updates via Scheduled Tasks: The rule may trigger on legitimate updates for older enterprise applications (e.g., legacy ERP systems or custom internal tools) that use ASProtect v123 RC1 for binary protection. These updates are often executed by Task Scheduler (taskschd.msc) or schtasks.exe during off-hours maintenance windows.
  • Filter/Exclusion: Exclude executions where the parent process is svchost.exe (specifically the Task Scheduler service) or schtasks.exe, and the file path resides in known legacy application directories (e.g., C:\Program Files\LegacyERP\).
• Antivirus/EDR Self-Scans and Real-Time Protection: During full system scans or real-time protection events, the EDR/AV engine may load or inspect ASProtect-protected binaries in memory or on disk. If the detection logic inspects file headers or memory sections, it can flag the protected executable as malicious during the scan process.
  • Filter/Exclusion: Exclude events where the parent process is the EDR/AV agent (e.g., MsMpEng.exe for Windows Defender, CrowdStrike Falcon services, or CrowdStrike Falcon sensor processes) and the action is a “Scan” or “Inspect” rather than an “Execute.”
• Installer Services for ASProtect-Protected Software: When installing or uninstalling software that includes ASProtect-protected components (e.g., certain DRM-protected media players, older Java applets, or specialized industrial control system software), the installer service (msiexec.exe or custom installers) may load the protected binary for registration or verification.
  • Filter/Exclusion: Exclude executions where the parent process is msiexec.exe or a known installer executable (e.g., setup.exe, install.exe) and