Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule detects the execution of specialized C# Red and Black team tools by identifying unique TypeLibGUID signatures often associated with reconnaissance or post-exploitation activities. Proactive hunting for these artifacts in Azure Sentinel is essential to distinguish legitimate security engineering operations from potential adversary use of similar custom C# utilities that may evade standard signature-based detection.

YARA Rule

rule HKTL_NET_GUID_BlockEtw {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/Soledge/BlockEtw"
        author = "Arnim Rupp"
        date = "2020-12-29"
    strings:
        $typelibguid0 = "daedf7b3-8262-4892-adc4-425dd5f85bca" 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/Soledge/BlockEtw
• Source Rule

False Positive Guidance

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

• Scenario: Legitimate deployment of Microsoft Office Add-ins or VSTO (Visual Studio Tools for Office) solutions.

  • Context: When users install custom C# add-ins for Excel, Word, or Outlook, the installation process generates specific TypeLib GUIDs that mimic those used by Red Team simulation tools (e.g., SharpView, Mimikatz wrappers).
  • Filter/Exclusion: Exclude processes where ImageName matches known Office application paths (e.g., EXCEL.EXE, WINWORD.EXE) and the parent process is a trusted installer (msiexec.exe or setup.exe).

• Scenario: Execution of Microsoft Endpoint Configuration Manager (SCCM) Client Agent tasks.

  • Context: SCCM often runs C# based maintenance scripts to update client agents, which instantiate COM objects with TypeLib GUIDs similar to those found in black-team forensics tools like SharpChk or PowerSploit.
  • Filter/Exclusion: Create an exclusion for the specific process name ccmexec.exe and its child processes running under the account NT SERVICE\CcmExec, provided the execution path is within the standard SCCM installation directory (C:\Program Files\Microsoft Configuration Manager).

• Scenario: Scheduled PowerShell jobs utilizing .NET assemblies for backup or reporting.

  • Context: Enterprise scheduled tasks (Task Scheduler) often invoke C# compiled DLLs or EXEs to generate daily compliance reports or perform database backups, triggering the detection logic due to shared TypeLib signatures with tools like Bloodhound or Ladon.
  • Filter/Exclusion: Filter alerts where the ParentProcessName is `sv