Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies the execution of specialized C# Red and Black team tools by analyzing unique TypeLibGUID values to distinguish legitimate security operations from potential adversary activity. Proactive hunting for these indicators in Azure Sentinel is essential to differentiate between authorized testing artifacts and malicious reconnaissance or tool deployment that may mimic standard administrative behavior.

YARA Rule

rule HKTL_NET_GUID_NoMSBuild {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/rvrsh3ll/NoMSBuild"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "034a7b9f-18df-45da-b870-0e1cef500215" ascii nocase wide
        $typelibguid1 = "59b449d7-c1e8-4f47-80b8-7375178961db" 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/rvrsh3ll/NoMSBuild
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the “Detects C# Red/Black-Team Tools via TypelibGUID” rule, including suggested filters and exclusions:

• Scenario: Automated Build Pipelines (Jenkins/GitLab CI)

  • Context: Continuous Integration servers often utilize C#-based build agents or custom plugins that instantiate COM objects to manage compilation artifacts. These agents frequently register specific TypelibGUIDs during the build process, mimicking the footprint of Red Team execution tools.
  • Filter/Exclusion: Create an exclusion for processes running under the service account (e.g., NT SERVICE\Jenkins or gitlab-runner) on dedicated CI/CD server hostnames. Additionally, filter out events where the parent process is a known build orchestrator like msbuild.exe or dotnet.exe.

• Scenario: Enterprise Endpoint Management (Microsoft Intune/SCCM)

  • Context: Configuration Manager (SCCM) and Microsoft Intune agents perform routine inventory scans and policy enforcement using C# components. These tools often load specific Type Libraries to interact with the Windows Registry or WMI, generating TypelibGUID events that resemble security tooling activity.
  • Filter/Exclusion: Exclude events where the parent process is ccmexec.exe (SCCM) or IntuneManagementExtension.exe. Furthermore, filter out GUIDs known to be associated with Microsoft Management Suite components by maintaining a whitelist of standard enterprise management GUIDs.

• Scenario: Scheduled PowerShell Automation Scripts

  • Context: IT operations teams frequently deploy scheduled tasks that run C# scripts (compiled into .exe or invoked via dotnet) for log rotation, backup verification, or health checks. These scripts often load specific COM libraries to interact with the OS, triggering the detection rule during their execution window.