Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This detection identifies the execution of known C# Red and Blue team utilities by analyzing unique TypeLibGUID signatures within Azure Sentinel logs. Proactive hunting for these artifacts is essential to distinguish legitimate security operations from potential adversary activity that mimics standard tooling to evade traditional signature-based defenses.

YARA Rule

rule HKTL_NET_GUID_SharpSecDump {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/G0ldenGunSec/SharpSecDump"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "e2fdd6cc-9886-456c-9021-ee2c47cf67b7" 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 3-5 specific false positive scenarios for the “Detects c# red/black-team tools via typelibguid” rule, including suggested filters and exclusions:

Scenario: Microsoft Office Deployment Tool (ODT) Execution
- Context: The Office Deployment Tool (setup.exe) is a widely used C# utility in enterprise environments for installing or updating Office suites. It frequently instantiates COM objects with specific typelibguid values that match the signature of red-team tools like SharpUp or similar enumeration scripts.
- Suggested Filter/Exclusion: Create an exclusion rule based on the parent process path and name: Process Name = "setup.exe" AND Path contains "\Microsoft Office\Office Deployment Tool". Alternatively, exclude specific known ODT GUIDs from the detection logic if they are static across versions.
Scenario: Scheduled PowerShell Task for .NET Framework Health Checks
- Context: Many organizations run scheduled tasks (via Task Scheduler) that execute C# scripts to monitor .NET framework health or patch compliance. These scripts often load specific type libraries (e.g., System.Management.Automation) which trigger the rule’s GUID detection logic, mimicking the behavior of tools like SharpHound or Bloodhound collectors.
- Suggested Filter/Exclusion: Exclude processes where the parent process is svchost.exe (specifically the “Task Scheduler” service) and the command line arguments contain keywords like HealthCheck, Compliance, or PatchStatus. A filter could be: Parent Process Name = "svchost.exe" AND Command Line contains "TaskScheduler".
Scenario: Endpoint Protection Agent Self-Update Routine
- Context: Modern EDR agents (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) utilize C# components to manage their own update cycles and policy synchronization