PeX 099 Eng bartCrackPl

Hunt Hypothesis

This rule identifies potential BartCrack password cracking tooling within PE files, indicating an adversary is actively attempting to recover plaintext credentials from memory dumps or saved hashes. Proactively hunting for this low-severity indicator allows the SOC to detect early-stage credential theft attempts in Azure Sentinel, enabling rapid containment before compromised accounts are leveraged for lateral movement or privilege escalation.

YARA Rule

rule PeX_099_Eng_bartCrackPl: PEiD
{
    strings:
        $a = { E9 F5 00 00 00 0D 0A C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 }
    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 legacy Java application (e.g., a custom internal CRM or ERP module) uses the bartCrackPl library or a similar cracklib-based password strength checker to validate user passwords during registration or password reset flows.

  • Filter/Exclusion: Exclude processes where the parent is a Java Virtual Machine (java.exe or jre/bin/java.exe) and the loaded module path contains cracklib or bartCrackPl in a known application directory (e.g., C:\Apps\InternalCRM\lib\).

• Scenario: A security team runs a scheduled PowerShell script to audit password complexity across the domain by invoking a native C# wrapper or a small utility that links against the bartCrackPl library to test sample passwords against the crack dictionary.

  • Filter/Exclusion: Exclude if the process is powershell.exe or pwsh.exe and the command line contains keywords like -Audit, -PasswordCheck, or -CrackTest, or if the process is launched from a specific security tooling directory (e.g., C:\SecOps\Tools\).

• Scenario: A developer or QA engineer tests a new authentication microservice locally on a build agent or dev workstation, where the service binary is linked against the bartCrackPl library for password validation.

  • Filter/Exclusion: Exclude if the host is in the Dev or Build AD group, or if the process path is within a known development workspace (e.g., C:\Users\<user>\Projects\ or C:\BuildAgents\).

• Scenario: A third-party backup or archiving tool (e.g., a custom wrapper for 7-Zip or a proprietary backup client) includes a password strength check feature that dynamically loads the bartCrackPl library when