Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt targets adversaries utilizing C#-based red or black team tools that generate unique TypeLibGUID artifacts to establish persistence or execute reconnaissance within the environment. Proactively hunting for these specific identifiers in Azure Sentinel is essential because they often indicate advanced tool usage that may bypass standard signature-based detections, allowing analysts to identify and analyze authorized versus unauthorized tooling before it impacts security posture.

YARA Rule

rule HKTL_NET_GUID_OffensiveCSharp {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/diljith369/OffensiveCSharp"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "6c3fbc65-b673-40f0-b1ac-20636df01a85" ascii nocase wide
        $typelibguid1 = "2bad9d69-ada9-4f1e-b838-9567e1503e93" ascii nocase wide
        $typelibguid2 = "512015de-a70f-4887-8eae-e500fd2898ab" ascii nocase wide
        $typelibguid3 = "1ee4188c-24ac-4478-b892-36b1029a13b3" ascii nocase wide
        $typelibguid4 = "5c6b7361-f9ab-41dc-bfa0-ed5d4b0032a8" ascii nocase wide
        $typelibguid5 = "048a6559-d4d3-4ad8-af0f-b7f72b212e90" ascii nocase wide
        $typelibguid6 = "3412fbe9-19d3-41d8-9ad2-6461fcb394dc" ascii nocase wide
        $typelibguid7 = "9ea4e0dc-9723-4d93-85bb-a4fcab0ad210" ascii nocase wide
        $typelibguid8 = "6d2b239c-ba1e-43ec-8334-d67d52b77181" ascii nocase wide
        $typelibguid9 = "42e8b9e1-0cf4-46ae-b573-9d0563e41238" ascii nocase wide
        $typelibguid10 = "0d15e0e3-bcfd-4a85-adcd-0e751dab4dd6" ascii nocase wide
        $typelibguid11 = "644dfd1a-fda5-4948-83c2-8d3b5eda143a" 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 12 string patterns in its detection logic.

References

False Positive Guidance

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

Scheduled Software Deployment via Microsoft Endpoint Configuration Manager (MECM/SCCM)
- Scenario: The SCCM client (ccmexec.exe) or its associated deployment agents frequently load C# assemblies to manage software updates. During scheduled maintenance windows, these tools generate typelibguid events that mimic the signature of Red Team reconnaissance tools because they utilize standard .NET reflection libraries for inventory scanning.
- Filter/Exclusion: Exclude processes originating from the C:\Windows\CCM\ directory or specifically filter out ccmexec.exe and smstsvc.exe when the parent process is the SCCM service account (e.g., NT SERVICE\SMS_EXECUTIVE).
Automated PowerShell Scripting for Compliance Audits
- Scenario: Enterprise IT teams often run scheduled PowerShell scripts (powershell.exe) to perform compliance checks or user access reviews. These scripts frequently invoke C# helper libraries (such as the Microsoft.PowerShell.Commands.Utility module) which instantiate specific TypeLib GUIDs associated with administrative tooling, triggering the detection logic intended for offensive security tools.
- Filter/Exclusion: Create an exclusion rule based on the command line arguments containing known internal script paths (e.g., C:\Scripts\Compliance\Audit.ps1) or exclude powershell.exe instances where the parent process is a scheduled task runner (svchost.exe with the “Schedule” service) running under a dedicated COMPUTER\IT-Audit-Admin account.
Visual Studio Build and Deployment Pipelines
- Scenario: In development environments, build servers (like Azure DevAgents or Jenkins nodes) compile C# applications using