Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging C#-based red and black team tools that expose unique typelibguid artifacts to establish persistence or conduct reconnaissance within Azure environments. Proactively hunting for these specific identifiers in Azure Sentinel is critical because they often represent early-stage tool deployment that may evade signature-based detection, allowing the SOC team to identify potential attacker infrastructure before it escalates into a full compromise.

YARA Rule

rule HKTL_NET_GUID_UrbanBishopLocal {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/slyd0g/UrbanBishopLocal"
        author = "Arnim Rupp"
        date = "2020-12-13"
    strings:
        $typelibguid0 = "88b8515e-a0e8-4208-a9a0-34b01d7ba533" 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/slyd0g/UrbanBishopLocal
• Source Rule

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 Enterprise Backup Jobs using VSS Writers

  • Scenario: Automated backup agents (e.g., Veeam Agent, Commvault, or Windows Server Backup) frequently invoke the Volume Shadow Copy Service (VSS). These C#-based services often instantiate specific TypelibGUIDs associated with COM interfaces to snapshot databases and file systems during nightly maintenance windows.
  • Filter/Exclusion: Create an exclusion for known backup service accounts (e.g., DOMAIN\VeeamBackupSvc, NT SERVICE\COMSys) executing processes named VeeamAgent.exe or wbengine.exe specifically between 01:00 and 06:00 local time.

• Microsoft Endpoint Configuration Manager (SCCM) Client Updates

  • Scenario: The SCCM/MECM client (ccmexec.exe) regularly performs inventory scans, software deployments, and OS updates. These tasks utilize C# components that load specific typelibraries to interact with the Windows Management Instrumentation (WMI) repository and manage application manifests, triggering the rule during standard deployment cycles.
  • Filter/Exclusion: Exclude events where the parent process is ccmexec.exe running under the NT AUTHORITY\SYSTEM or DOMAIN\SCCMClient account, and the command line contains arguments related to “Inventory,” “Deployment,” or “SoftwareUpdate.”

• ITSM Ticketing System Agents (e.g., ServiceNow CSD)

  • Scenario: Endpoint agents for IT service management platforms like ServiceNow Customer Service Desk (CSD) or BMC Helix Discovery run as background services. These agents use C# libraries to poll system health, collect asset data