Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt targets adversaries leveraging C#-based red and black team tools that expose unique TypeLibGUID artifacts to evade standard signature-based detection. Proactively hunting for these specific GUIDs in Azure Sentinel is critical because they often indicate advanced reconnaissance or post-exploitation activities that may otherwise remain invisible within the low-severity noise of routine application behavior.

YARA Rule

rule HKTL_NET_GUID_AVIator {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/Ch0pin/AVIator"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "4885a4a3-4dfa-486c-b378-ae94a221661a" 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 rule “Detects C# Red/Black-Team Tools via TypelibGUID”, including suggested filters and exclusions:

Scenario: Automated Software Deployment via SCCM or Intune
- Context: Enterprise deployment agents (e.g., Microsoft Endpoint Configuration Manager, Microsoft Intune) frequently utilize C# scripts to install updates or manage inventory. These processes often load specific .NET assemblies that match the TypelibGUID signatures of security tools during the installation phase.
- Suggested Filter/Exclusion: Create an exclusion for the parent process paths associated with deployment agents (e.g., C:\Windows\CCM\CcmExec.exe, C:\Program Files\Microsoft Intune Management Extension\IntuneManagementExtension.exe) and restrict the alert to specific user contexts (e.g., NT AUTHORITY\SYSTEM or DOMAIN\DeployServiceAccount).
Scenario: Scheduled Antivirus Definition Updates
- Context: Third-party Endpoint Detection and Response (EDR) or antivirus solutions often run scheduled jobs to update virus definitions. These background services are frequently built on the .NET framework and may instantiate C# components that generate TypelibGUID events indistinguishable from active red/black team reconnaissance tools.
- Suggested Filter/Exclusion: Exclude known security vendor processes (e.g., MsMpEng.exe, SentinelOneAgent.exe, CrowdStrikeService.exe) and filter by the specific CommandLine arguments that indicate a routine update task rather than an interactive tool execution.
Scenario: Internal IT Helpdesk Ticketing System Integration
- Context: Many organizations use custom C# applications or plugins within their Service Desk platforms (e.g., ServiceNow, Jira, or internal ticketing systems) to automate asset discovery. When these agents scan endpoints for hardware