Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule detects the execution of C#-based red and black team tools by identifying their unique TypeLibGUID signatures within process events. A SOC team should proactively hunt for these indicators in Azure Sentinel to distinguish legitimate security tooling from potential adversary activity that mimics standard development environments, thereby reducing false positives during incident response.

YARA Rule

rule HKTL_NET_GUID_Keylogger {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/BlackVikingPro/Keylogger"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "7afbc9bf-32d9-460f-8a30-35e30aa15879" 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/BlackVikingPro/Keylogger
• 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: Automated Build Pipeline Execution

  • Context: Continuous Integration/Continuous Deployment (CI/CD) servers (e.g., Jenkins, Azure DevOps, GitHub Actions) frequently compile .NET applications. During the build process, tools like msbuild.exe or dotnet.exe load C# assemblies that register specific TypeLibGUIDs associated with Red Team frameworks (such as Covenant or SharpUp) used within the pipeline’s internal libraries.
  • Filter/Exclusion: Exclude processes running under the CI/CD service account (e.g., AZUREDEVOPS-BUILD-SVC or JENKINS-AGENT) on specific build server hostnames. Additionally, filter out events where the parent process is a known build orchestrator (msbuild.exe, dotnet.exe) and the command line contains keywords like /restore or /publish.

• Scenario: Endpoint Antivirus Heuristic Scanning

  • Context: Modern EDR/Anti-malware solutions (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) utilize C# based modules to perform heuristic analysis. When scanning a directory containing Red Team tool binaries or .NET dependencies, the AV engine may instantiate these tools’ TypeLibGUIDs in memory to verify signatures, triggering the rule even though no active attack simulation is occurring.
  • Filter/Exclusion: Create an exclusion for processes belonging to known security vendors (e.g., C:\Program Files\CrowdStrike\csagent.exe, C:\Windows\System32\MpCmdRun.exe). Filter events where the process path resides within standard vendor installation directories and the user context is a system service account.

• **Scenario: Scheduled PowerShell Inventory