Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule detects the execution of specialized C# Red and Black team security tools by identifying unique TypeLibGUID signatures within Azure Sentinel logs. Proactive hunting for these specific tool behaviors is essential to distinguish legitimate security operations from potential adversary activity that mimics known security utilities to evade detection.

YARA Rule

rule HKTL_NET_GUID_p0wnedShell {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/Cn33liz/p0wnedShell"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "2e9b1462-f47c-48ca-9d85-004493892381" 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/Cn33liz/p0wnedShell
• Source Rule

False Positive Guidance

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

• Scenario: Automated CI/CD Pipeline Execution

  • Context: Build agents (e.g., Azure DevOps or Jenkins) running .NET-based build tasks often instantiate C# assemblies that share TypelibGUID signatures with known offensive tools like BloodHound or SharpUp. These agents frequently execute in a dedicated service account context.
  • Filter/Exclusion: Exclude processes launched by specific CI/CD service accounts (e.g., SYSTEM, AZDO-BuildAgent) and restrict the rule to only trigger on interactive user sessions (LogonType 2 or 3) rather than batch job contexts.

• Scenario: Endpoint Management Suite Updates

  • Context: Enterprise endpoint management solutions like Microsoft Intune, SCCM (Configuration Manager), or CrowdStrike Falcon utilize C# components for policy enforcement and inventory scanning. Their background services often load libraries with TypelibGUID values identical to reconnaissance tools such as PowerView or Lazagne.
  • Filter/Exclusion: Create a whitelist of known benign process names (e.g., CcmExec.exe, IntuneManagementExtension.exe) and their parent processes, ensuring the rule ignores any detection where the ParentImage matches these enterprise management binaries.

• Scenario: Scheduled PowerShell Health Checks

  • Context: IT operations teams often deploy scheduled tasks (Task Scheduler) that run custom C# scripts for health monitoring or compliance auditing. These scripts may utilize the same underlying .NET libraries as SharpHound or Rubeus, triggering the rule during off-hours when no red-team activity is expected.
  • Filter/Exclusion: