Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies potential adversary activity by detecting C#-based red and blue 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 operations and malicious tool usage that may mimic standard administrative behavior, thereby reducing false positives while uncovering stealthy threat actor presence.

YARA Rule

rule HKTL_NET_GUID_SharpClipHistory {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/FSecureLABS/SharpClipHistory"
        author = "Arnim Rupp"
        date = "2020-12-21"
    strings:
        $typelibguid0 = "1126d5b4-efc7-4b33-a594-b963f107fe82" 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/FSecureLABS/SharpClipHistory
• Source Rule

False Positive Guidance

Here are 3-5 specific false positive scenarios for the rule “Detects c# red/black-team tools via typelibguid”, including suggested filters and exclusions:

• Scenario: Automated CI/CD Pipeline Execution

  • Context: Continuous Integration servers (e.g., Jenkins, Azure DevOps, GitHub Actions) frequently compile C# applications or run unit tests using dotnet CLI tools. These processes often instantiate .NET assemblies that register specific TypeLibGUIDs similar to those used by Red Team emulation frameworks (like Atomic Red Team).
  • Suggested Filter/Exclusion: Exclude the process names of known CI agents and build tools from the detection logic.
    • Filter: ProcessName IN ("dotnet.exe", "msbuild.exe", "jenkins-agent.exe") AND CommandLine CONTAINS "/t:Build" OR "/t:Test".

• Scenario: Scheduled Antivirus or EDR Scanning

  • Context: Enterprise Endpoint Detection and Response (EDR) agents often utilize C# libraries for deep inspection or heuristic scanning. When the agent scans a .NET application directory, it may trigger the TypeLibGUID registration event that mimics Red Team tool deployment.
  • Suggested Filter/Exclusion: Create an exclusion based on the parent process of major security vendors to distinguish between active threat hunting and routine maintenance.
    • Filter: ParentProcessName IN ("SentinelOne.exe", "CrowdStrikeService.exe", "McAfeeHostAgent.exe") AND EventID = 4688 (New Process Creation).

• Scenario: Office 365 ProPlus Add-in Initialization

  • Context: Microsoft Office applications (Word, Excel) load various C#-based add-ins and COM components upon user login or document opening. These add-ins often register