Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies potential adversary activity by detecting the presence of known C# red and black team tools through their unique TypeLibGUID signatures within Azure Sentinel logs. Proactively hunting for these indicators allows the SOC team to distinguish between legitimate security testing operations and unauthorized tool usage that could signal a stealthy threat actor leveraging similar frameworks.

YARA Rule

rule HKTL_NET_GUID_SharpShares {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/djhohnstein/SharpShares/"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "fe9fdde5-3f38-4f14-8c64-c3328c215cf2" 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 1 string patterns in its detection logic.

References

• https://github.com/djhohnstein/SharpShares/
• 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: Legitimate Automated Patching via Microsoft Endpoint Configuration Manager (MECM/SCCM)

  • Context: During scheduled maintenance windows, SCCM agents on Windows 10/11 endpoints execute C#-based deployment scripts to install patches or software. These scripts often instantiate COM objects with specific typelibguid values that overlap with known security tool signatures (e.g., Microsoft.Update.Core).
  • Suggested Filter: Exclude processes where the executable path matches C:\Program Files\Microsoft Configuration Manager\AdminConsole\* and the parent process is ccmsetup.exe or WmiPrvSE.exe.

• Scenario: Internal DevOps Build Pipelines (Azure DevOps / Jenkins Agents)

  • Context: Enterprise build agents running on Windows servers frequently utilize C# libraries to compile code, manage dependencies, or run unit tests. Tools like dotnet CLI, MSBuild, or custom internal CI/CD agents often load type libraries that trigger this rule during nightly builds.
  • Suggested Filter: Create an exclusion for processes running under the service account NT SERVICE\TeamFoundationBuildAgent (or specific Azure DevOps build agent accounts) where the command line contains arguments like /restore, /build, or /test.

• Scenario: Enterprise Antivirus and EDR Scanning Engines

  • Context: Major security suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, SentinelOne) utilize C# components for their real-time scanning engines or policy management modules. These components frequently register type libraries that mimic the GUIDs of red-team tools like BloodHound or SharpUp.
  • **Suggested