Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis identifies the execution of specialized C# Red and Black team tools by analyzing unique TypelibGUID signatures within Azure Sentinel logs. Proactively hunting for these indicators allows the SOC to distinguish between legitimate security testing activities and potential adversary reconnaissance or tool deployment that mimics trusted internal utilities.

YARA Rule

rule HKTL_NET_GUID_MiscTools {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/rasta-mouse/MiscTools"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "384e9647-28a9-4835-8fa7-2472b1acedc0" ascii nocase wide
        $typelibguid1 = "d7ec0ef5-157c-4533-bbcd-0fe070fbf8d9" ascii nocase wide
        $typelibguid2 = "10085d98-48b9-42a8-b15b-cb27a243761b" ascii nocase wide
        $typelibguid3 = "6aacd159-f4e7-4632-bad1-2ae8526a9633" ascii nocase wide
        $typelibguid4 = "49a6719e-11a8-46e6-ad7a-1db1be9fea37" 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 5 string patterns in its detection logic.

References

• https://github.com/rasta-mouse/MiscTools
• Source Rule

False Positive Guidance

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

• Scenario: Automated CI/CD Build Pipelines

  • Context: Enterprise build servers (e.g., Jenkins, Azure DevOps) frequently execute C# compilation tasks using msbuild.exe or dotnet.exe. These processes often load standard .NET assemblies that generate the specific TypeLibGUIDs associated with Red Team tools during the build artifact generation phase.
  • Filter/Exclusion: Create an exclusion for process images matching known build agents (e.g., C:\Program Files\Microsoft Visual Studio\*\MSBuild\Bin\msbuild.exe) running under service accounts like SYSTEM or specific CI/CD identities (e.g., AZURE-AD-BUILD-SVC).

• Scenario: Scheduled Office 365 Configuration Scripts

  • Context: IT Operations teams often run scheduled PowerShell scripts to manage Exchange or Teams configurations. These scripts utilize C# libraries (such as the Microsoft Graph SDK) which instantiate TypeLibGUIDs identical to those used by Red Team reconnaissance tools like SharpView or Bloodhound.
  • Filter/Exclusion: Exclude events where the parent process is powershell.exe and the command line contains keywords related to Office 365 management (e.g., -ImportModule Microsoft.Online.*, Connect-MicrosoftTeams) during business hours (08:00–18:00).

• Scenario: Endpoint Management Agent Updates

  • Context: Unified endpoint management platforms like Microsoft Intune or SCCM utilize C# components to push configuration updates and inventory scans. The background service ccmexec.exe often loads .NET assemblies that trigger the same TypeLibGUID signatures as Black Team monitoring tools