Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging C#-based red and black team tools that generate unique typelibguid artifacts to execute reconnaissance or post-exploitation tasks within the Azure environment. Proactively hunting for these specific GUIDs in Azure Sentinel allows the SOC team to distinguish legitimate security tooling from malicious activity, ensuring early identification of potential lateral movement or data exfiltration attempts disguised as standard administrative operations.

YARA Rule

rule HKTL_NET_GUID_RuralBishop {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/rasta-mouse/RuralBishop"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "fe4414d9-1d7e-4eeb-b781-d278fe7a5619" 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

False Positive Guidance

Here are 5 specific false positive scenarios for the “Detects C# Red/Black-Team Tools via TypelibGUID” rule, along with recommended filters or exclusions:

Scenario: Automated Deployment of Microsoft Teams or Office Add-ins
- Context: Enterprise IT frequently deploys or updates Microsoft Teams and various Office Add-ins using PowerShell scripts. These C# applications register specific TypelibGUIDs (e.g., {000209FF-0000-0000-C000-000000000046} for Excel or Teams-specific GUIDs) during installation or background update cycles.
- Filter/Exclusion: Create an exclusion rule that ignores alerts where the ParentProcessName is msiexec.exe, powershell.exe, or setup.exe AND the CommandLine contains keywords like /quiet, /norestart, or specific deployment package IDs (e.g., TeamsUpdatePackage).
Scenario: Scheduled Antivirus Definition Updates via C# Agents
- Context: Many endpoint protection suites (such as CrowdStrike Falcon, Carbon Black, or custom EDR agents) utilize C# components to manage definition updates. These scheduled jobs often instantiate COM objects with unique TypelibGUIDs that match the signature of Red/Black team reconnaissance tools used for lateral movement analysis.
- Filter/Exclusion: Exclude events originating from known security vendor service accounts (e.g., NT SERVICE\CrowdStrikeService) or specific process paths located in C:\Program Files\<VendorName>\ where the ProcessID matches a scheduled task ID associated with “Definition Update” or “Agent Heartbeat.”
Scenario: Enterprise Document Management and E-Signature Integration
- Context: Organizations using tools like DocuSign,