Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis identifies potential adversary activity by detecting C#-based red and black team tools through their unique TypeLibGUID signatures within Azure Sentinel logs. Proactively hunting for these specific identifiers allows the SOC team to distinguish between legitimate security operations and malicious tool usage that may mimic standard administrative behavior, thereby reducing false positives during incident response.

YARA Rule

rule HKTL_NET_GUID_SolarFlare {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/mubix/solarflare"
        author = "Arnim Rupp"
        date = "2020-12-15"
    strings:
        $typelibguid0 = "ca60e49e-eee9-409b-8d1a-d19f1d27b7e4" 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/mubix/solarflare
• 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 Build & Release Pipelines

  • Context: CI/CD agents (e.g., Jenkins, Azure DevOps) running on build servers frequently instantiate .NET processes to compile code or run unit tests. These processes often load standard C# libraries that match the specific TypelibGUID signatures used by Red Team tools like Cobalt Strike Beacon or Mimikatz.
  • Filter/Exclusion: Create a process exclusion based on the parent process name (e.g., msbuild.exe, dotnet.exe) and restrict the detection to exclude events where the parent image path contains \BuildAgent\ or \AzureDevOps\.

• Scenario: Enterprise Endpoint Management Agents

  • Context: System administrators use tools like Microsoft SCCM (Configuration Manager) or Ivanti Neurons to push software updates and inventory scans. These agents utilize C# components for remote management tasks, which generate TypelibGUID events identical to those generated by Black Team forensic tools like Velociraptor or Sysmon.
  • Filter/Exclusion: Exclude alerts where the running process name matches known enterprise agent binaries (e.g., ccmexec.exe, IvantiAgent.exe) and the user context is a local system account (NT AUTHORITY\SYSTEM) rather than an interactive user.

• Scenario: Scheduled PowerShell Backup Jobs

  • Context: Nightly scheduled tasks run PowerShell scripts to back up Active Directory or export logs. These scripts often invoke C# assemblies (e.g., System.Management.Automation) that register specific TypeLib GUIDs, triggering the rule even though no Red Team activity is occurring