codeCrypter 031 Tibbar additional

Hunt Hypothesis

This hypothesis targets the execution of Tibbar, a known code crypter and packer, which adversaries frequently use to obfuscate malicious payloads and evade static analysis. Proactively hunting for this specific variant in Azure Sentinel allows the SOC to identify potential initial access or lateral movement activities that may be hidden by complex packing techniques before they trigger higher-severity alerts.

YARA Rule

rule codeCrypter_031_Tibbar_additional: PEiD
{
    strings:
        $a = { 50 58 53 5B 90 BB ?? ?? ?? 00 FF E3 90 CC CC CC 55 8B EC 5D C3 CC CC CC CC CC CC CC CC CC CC CC }
    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 or DevOps engineer uses a custom Python or C# script to obfuscate configuration files or small utility modules before packaging them into a release artifact, utilizing a library that implements the specific “Tibbar” encryption pattern.
  • Filter/Exclusion: Exclude processes originating from development IDEs (e.g., code.exe, idea64.exe, devenv.exe) or specific scripting interpreters (python.exe, dotnet.exe) when the parent process is a known build tool (e.g., msbuild.exe, npm.exe, gradle.exe).
• Scenario: An automated scheduled task runs a proprietary internal tool (e.g., license_manager.exe or config_encryptor.exe) that encrypts local state files or API keys using the Tibbar algorithm to prevent plaintext leakage in shared network drives.
  • Filter/Exclusion: Exclude processes with names matching known internal utility patterns (e.g., *encrypt*, *crypt*, *license*) that are launched by Task Scheduler (svchost.exe with SchedSvc service) or cron/at equivalents, specifically if the working directory is a known application data folder (e.g., C:\ProgramData\InternalTools\).
• Scenario: A security team performs a periodic integrity check or baseline scan using a custom YARA-based validation script that loads sample binaries into memory to verify they match the expected encrypted signature, inadvertently triggering the detection on the test harness process.
  • Filter/Exclusion: Exclude processes where the command line arguments contain keywords like --validate, --check, or --test, or where the parent process is a known security scanner (e.g., yara.exe, clamscan.exe, malwarebytes.exe).
• Scenario: A Java