Detects .NET red/black-team tools via typelibguid

Hunt Hypothesis

This hunt hypothesis identifies adversaries leveraging custom or known .NET-based Red and Black team tools by analyzing unique TypelibGUID signatures within process execution events. Proactively hunting for these indicators in Azure Sentinel is essential to distinguish legitimate security tooling from malicious .NET payloads that may mimic trusted applications to evade standard detection rules.

YARA Rule

rule HKTL_NET_GUID_LockLess {
    meta:
        description = "Detects .NET red/black-team tools via typelibguid"
        reference = "https://github.com/GhostPack/LockLess"
        author = "Arnim Rupp"
        date = "2021-01-21"
    strings:
        $typelibguid0 = "a91421cb-7909-4383-ba43-c2992bbbac22" 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/GhostPack/LockLess
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Detects .NET red/black-team tools via typelibguid rule, including suggested filters and exclusions:

• Scenario: Microsoft Endpoint Configuration Manager (SCCM) Client Updates

  • Context: The SCCM client (ccmsetup.exe or CcmExec.exe) frequently invokes .NET assemblies during software deployment and inventory scans. These processes often register standard COM type libraries that match the typelibguids associated with common red-team tools like SharpUp or PowerSploit.
  • Filter/Exclusion: Exclude process paths containing \Microsoft Configuration Manager\ and specifically filter out CcmExec.exe when the parent process is WmiPrvSE.exe.

• Scenario: Scheduled Backup Jobs Using PowerShell

  • Context: Enterprise backup solutions (e.g., Veeam, Commvault) or custom maintenance scripts often run scheduled tasks that load .NET libraries for file system enumeration. If these scripts utilize the same underlying COM interfaces as tools like BloodHound or Lateral Movement Toolkit, they trigger the rule during their nightly execution window.
  • Filter/Exclusion: Create an exclusion based on the Scheduled Task Name (e.g., “NightlyBackup” or “InventorySync”) and restrict detection to business hours only, excluding runs between 02:00 and 05:00 UTC.

• Scenario: Visual Studio Build Agents on CI/CD Servers

  • Context: In environments where developers run builds directly on enterprise workstations or dedicated build agents (e.g., Azure DevOps Agents), the .NET runtime loads various type libraries during compilation and testing phases. These often mimic the typelibguid signatures of forensic tools like Kape or Mimikatz.
  • **Filter/Exclusion