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 unique TypeLibGUID signatures within Azure Sentinel logs. Proactive hunting for these indicators is essential to distinguish legitimate security operations from malicious tooling that adversaries may deploy to establish persistence or evade detection in the environment.

YARA Rule

rule HKTL_NET_GUID_azure_password_harvesting {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/guardicore/azure_password_harvesting"
        author = "Arnim Rupp"
        date = "2020-12-21"
    strings:
        $typelibguid0 = "7ad1ff2d-32ac-4c54-b615-9bb164160dac" 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/guardicore/azure_password_harvesting
• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the “Detects C# Red/Black-Team Tools via TypelibGUID” rule, including tailored filters and exclusions:

• Scenario: Automated CI/CD Pipeline Execution

  • Context: Internal build agents (e.g., Jenkins, Azure DevOps, or GitHub Actions runners) frequently compile .NET solutions using msbuild.exe or dotnet.exe. These processes often load standard C# runtime assemblies that share the same TypelibGUIDs as Red/Black team tools during compilation and testing phases.
  • Filter/Exclusion: Exclude process paths matching known build agent directories (e.g., C:\Program Files\Microsoft Visual Studio\*\MSBuild\* or D:\GitHubActions\_runner\*) and limit detection to specific user accounts like SYSTEM, BUILD-SERVICE-ACCOUNT, or GITHUB-ACTORS.

• Scenario: Scheduled .NET Framework Health Checks

  • Context: Enterprise monitoring suites (such as SolarWinds, Datadog Agent, or custom PowerShell scripts) run scheduled jobs every hour to query application health. These agents utilize C# libraries that instantiate the same TypelibGUIDs used by security testing tools while probing network endpoints and database connections.
  • Filter/Exclusion: Create a rule exclusion for processes running under specific service accounts (e.g., DOMAIN\Monitoring-Svc) executing from known monitoring installation paths, such as C:\Program Files\SolarWinds\* or C:\ProgramData\Datadog\Agent\bin\.

• Scenario: Office 365 / Microsoft Teams Background Updaters

  • Context: The Microsoft Office Click-to-Run service and Teams background processes often load C# components for add-in management and telemetry. These components utilize standard .NET TypelibGUIDs