Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging C# red and black team tools that register unique TypeLibGUIDs to establish a foothold or conduct reconnaissance within the environment. Proactively hunting for these specific identifiers in Azure Sentinel allows the SOC team to distinguish legitimate administrative activity from potential tool deployment by threat actors, ensuring early visibility into low-severity but high-impact operational changes.

YARA Rule

rule HKTL_NET_GUID_Naga {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/byt3bl33d3r/Naga"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "99428732-4979-47b6-a323-0bb7d6d07c95" ascii nocase wide
        $typelibguid1 = "a2c9488f-6067-4b17-8c6f-2d464e65c535" 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/byt3bl33d3r/Naga
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the “Detects c# red/black-team tools via typelibguid” rule, along with suggested filters and exclusions:

• Scenario: Automated Build Pipeline Execution

  • Context: Continuous Integration/Continuous Deployment (CI/CD) agents (e.g., Azure DevOps or Jenkins running on Windows) frequently invoke .NET-based build tools like MSBuild or NuGet.exe. These tools generate specific TypeLib GUIDs during compilation and package restoration that mimic the signatures of Red Team automation frameworks.
  • Filter/Exclusion: Exclude processes located in standard CI agent directories (e.g., C:\Program Files\Microsoft Visual Studio\..., C:\Jenkins\workspace\) or filter by process parent name matching known build agents (TaskAgentService.exe, java.exe running Maven).

• Scenario: Endpoint Protection Policy Updates

  • Context: Enterprise EDR solutions (such as CrowdStrike Falcon, Microsoft Defender for Endpoint, or Carbon Black) utilize C# components to push policy updates and perform health checks. The background service responsible for these updates often instantiates a .NET assembly with a TypeLib GUID that overlaps with the detection logic for security testing tools.
  • Filter/Exclusion: Whitelist specific process paths belonging to known EDR vendors (e.g., C:\Program Files\CrowdStrike\..., C:\ProgramData\Microsoft\Windows Defender\...) and exclude events where the parent process is the primary EDR service daemon.

• Scenario: Scheduled Office 365 Management Tasks

  • Context: IT administrators often deploy scheduled PowerShell jobs or background services using C# libraries to manage Exchange Online or SharePoint configurations (e.g., Microsoft.Online.SharePoint.PowerShell). These management tools utilize TypeLib GUIDs identical to those used by Red