CRYPToCRACks PE Protector v093 Lucas Fleischer h

Hunt Hypothesis

This rule identifies executable files packed with the CRYPToCRACks PE Protector, a tool frequently used by threat actors to obfuscate malicious payloads and evade static analysis during initial access or execution phases. Proactively hunting for this specific packer in Azure Sentinel allows the SOC to uncover stealthy implant deployments or trojanized binaries that may have slipped past standard signature-based detections, ensuring early visibility into low-severity but potentially persistent threats.

YARA Rule

rule CRYPToCRACks_PE_Protector_v093_Lucas_Fleischer_h: PEiD
{
    strings:
        $a = { 5B 81 E3 00 FF FF FF 66 81 3B 4D 5A 75 33 8B F3 03 73 3C 81 3E 50 45 00 00 75 26 0F B7 46 18 8B C8 69 C0 AD 0B 00 00 F7 E0 2D AB 5D 41 4B 69 C9 DE C0 00 00 03 C1 75 09 83 EC 04 0F 85 DD 00 00 00 81 EB 00 01 00 00 75 BE 90 72 ?? ?? ?? ?? 00 00 00 00 00 00 00 7A ?? ?? ?? 72 ?? ?? ?? ?? 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ?? ?? ?? ?? 00 00 00 00 6B 65 72 6E 65 6C 33 32 2E 64 6C 6C 00 C1 00 46 61 74 61 6C 45 78 69 74 }
    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

• Scenario: A developer is testing a new microservice built with the .NET Framework or C++ that utilizes the CryptoCracks PE Protector (v093) for obfuscation and anti-debugging features during the staging phase. The binary is executed directly from a development workstation or a CI/CD build agent rather than a production server.

  • Filter/Exclusion: Exclude execution paths containing \dev\, \staging\, or \build\ directories. Additionally, exclude processes where the parent process is dotnet.exe, msbuild.exe, or code.exe (VS Code) to account for IDE-launched debugging sessions.

• Scenario: An IT administrator is manually deploying a legacy line-of-business application that was historically protected with this specific version of CryptoCracks to maintain compatibility with older hardware. The executable is run from a network share or a temporary extraction folder (C:\Temp\ or \\fileserver\apps\) during the deployment script execution.

  • Filter/Exclusion: Exclude paths matching C:\Temp\, C:\Users\*\AppData\Local\Temp\, or network share paths like \\fileserver\. Also, consider whitelisting the specific SHA256 hash of the known legacy binary if it remains static across deployments.

• Scenario: A security team is performing a controlled test of their EDR/AV detection capabilities by executing a known good (or intentionally obfuscated) sample binary in an isolated lab environment or a dedicated “canary” host. The binary is stored in a dedicated test directory and executed by a scheduled task or manual command.

  • Filter/Exclusion: Exclude execution from paths containing \security-tests\, \edr-lab\, or \canary\. Alternatively, exclude hosts tagged in the asset management system (e.g., CMDB) with the tag `