ASProtectv123RC1

Hunt Hypothesis

This rule identifies the presence of ASProtect v1.23 RC1, a commercial software packer frequently abused by threat actors to obfuscate malicious payloads and evade static analysis. Proactively hunting for this specific version allows the SOC to uncover hidden executables or dropped files that may be leveraging this packer to conceal malicious code within the Azure environment.

YARA Rule

rule ASProtectv123RC1
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 01 [2] 00 E8 01 00 00 00 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 Application Packaging and Installer Creation

  • Scenario: Developers or IT support staff use ASProtect to pack executable files (.exe, .dll) for legacy Windows applications or third-party installers that require anti-debugging or size reduction. The packed binary is often scanned by AV or EDR agents during the build or deployment phase.
  • Filter/Exclusion: Exclude files located in specific build directories (e.g., C:\Builds\LegacyApps\, C:\Temp\Installers\) or exclude processes like MSIEXEC.EXE or INSETUP.EXE when the file path matches known installer staging areas.

• Third-Party Vendor Tools with Packed Binaries

  • Scenario: Enterprise software vendors (e.g., backup agents, monitoring tools, or specialized hardware drivers) ship executables packed with ASProtect to protect IP or reduce size. When these tools are installed or updated, the packed binaries are written to disk and trigger the YARA rule.
  • Filter/Exclusion: Maintain a whitelist of known vendor directories (e.g., C:\Program Files\AcmeBackup\, C:\Program Files\ZabbixAgent\) and exclude files within these paths if the file signature or version matches the expected vendor release.

• Scheduled Maintenance Jobs with Packed Scripts/Executables

  • Scenario: IT operations teams schedule PowerShell or batch jobs that execute small, packed helper utilities (e.g., disk cleanup scripts, log rotation tools) that were packed with ASProtect to prevent tampering. These jobs run via Task Scheduler or cron equivalents and may be scanned during execution.
  • Filter/Exclusion: Exclude files executed by SVCHOST.EXE or TASKENG.EXE (Task Scheduler service) if the file path is