Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis identifies potential adversary activity by detecting C# red and black team tools through their unique TypeLibGUID signatures within Azure Sentinel logs. Proactively hunting for these specific tool identifiers allows the SOC team to distinguish between legitimate security operations and suspicious reconnaissance or post-exploitation activities that may otherwise blend into routine system noise.

YARA Rule

rule HKTL_NET_GUID_KeeThief {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/GhostPack/KeeThief"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid1 = "39aa6f93-a1c9-497f-bad2-cc42a61d5710" ascii nocase wide
        $typelibguid3 = "3fca8012-3bad-41e4-91f4-534aa9a44f96" ascii nocase wide
        $typelibguid4 = "ea92f1e6-3f34-48f8-8b0a-f2bbc19220ef" ascii nocase wide
        $typelibguid5 = "c23b51c4-2475-4fc6-9b3a-27d0a2b99b0f" ascii nocase wide
        $typelibguid6 = "94432a8e-3e06-4776-b9b2-3684a62bb96a" ascii nocase wide
        $typelibguid7 = "80ba63a4-7d41-40e9-a722-6dd58b28bf7e" 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 6 string patterns in its detection logic.

References

• https://github.com/GhostPack/KeeThief
• Source Rule

False Positive Guidance

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

• Scenario: Automated Build & Deployment Pipelines

  • Context: CI/CD agents (e.g., Jenkins, Azure DevOps, GitHub Actions) running on build servers frequently instantiate C# libraries to compile code or execute unit tests. Tools like MSBuild, NuGet, and Octopus Deploy often load specific TypeLibGUIDs associated with .NET testing frameworks (like xUnit or NUnit) which mimic the signatures of Red/Blue team reconnaissance tools.
  • Filter/Exclusion: Create an exclusion based on the ProcessName being part of a known build service list (msbuild.exe, dotnet.exe, jenkins-agent.exe) AND the ParentProcessName belonging to the CI orchestrator (e.g., VSTS.Agent.exe).

• Scenario: Scheduled Endpoint Management Tasks

  • Context: Enterprise management suites such as Microsoft SCCM (Configuration Manager) or Ivanti Neurons perform regular inventory scans and patch compliance checks. These agents utilize C# components to query system metadata, triggering the same TypeLibGUIDs used by security assessment tools like Nmap or BloodHound.
  • Filter/Exclusion: Exclude events where the UserAccount is a dedicated service account (e.g., NT SERVICE\CCMExec, IvantiAgent) and the execution occurs within a defined maintenance window (e.g., 02:00–04:00 UTC).

• Scenario: Internal Developer Workstations

  • Context: Software engineers on internal networks running Visual Studio 2019/2022 or JetBrains Rider often load debugging extensions