Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies the execution of specialized C# Red and Black team security tools by analyzing unique TypeLibGUID signatures within Azure Sentinel logs. Proactively hunting for these indicators allows the SOC to distinguish between legitimate security operations and potential adversary activity that mimics trusted tooling patterns, thereby reducing false positives and enhancing visibility into internal threat landscape exercises.

YARA Rule

rule HKTL_NET_GUID_LethalHTA {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/codewhitesec/LethalHTA"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "784cde17-ff0f-4e43-911a-19119e89c43f" ascii nocase wide
        $typelibguid1 = "7e2de2c0-61dc-43ab-a0ec-c27ee2172ea6" ascii nocase wide
    condition:
        (uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550) and any of them
}

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 2 string patterns in its detection logic.

References

• https://github.com/codewhitesec/LethalHTA
• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the “Detects c# red/black-team tools via typelibguid” rule, including suggested filters and exclusions:

• Scenario: Automated Patch Management Deployment

  • Context: Enterprise patch management solutions (e.g., Microsoft Endpoint Configuration Manager (SCCM) or Ivanti) often utilize C# agents to scan system components. During a scheduled maintenance window, these agents instantiate .NET assemblies that generate specific typelibguid values identical to those used by Red Team reconnaissance tools like BloodHound or SharpUp.
  • Suggested Filter/Exclusion: Create an exclusion rule for the process image path of known patch management services (e.g., C:\Program Files\Microsoft Configuration Manager\ or C:\Program Files\Ivanti\) and restrict detection to non-maintenance windows (e.g., exclude events occurring between 02:00–04:00 UTC).

• Scenario: Internal DevOps Build Pipelines

  • Context: CI/CD pipelines running on build agents (e.g., Azure DevOps Agents, Jenkins, or GitLab Runners) frequently execute C# scripts to compile code, run unit tests, or package artifacts. These processes often load standard .NET libraries that match the typelibguid signatures of Black Team tools like SharpChat or PowerShell Empire.
  • Suggested Filter/Exclusion: Exclude events where the parent process is a known build agent service (e.g., VSTest.exe, dotnet.exe running under the SYSTEM or specific BuildService user accounts) and filter by the build server’s IP address range.

• Scenario: Enterprise Antivirus Real-Time Scanning

  • Context: Next-Generation Antivirus (NGAV