Detects .NET red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies the execution of specialized .NET-based red and black team reconnaissance or attack tools by analyzing unique typelib GUID signatures within Azure Sentinel logs. Proactively hunting for these indicators allows SOC teams to distinguish between legitimate administrative activity and potential adversary presence utilizing custom .NET frameworks, thereby reducing false positives and accelerating incident response times.

YARA Rule

rule HKTL_NET_GUID_EasyNet {
    meta:
        description = "Detects .NET red/black-team tools via typelibguid"
        reference = "https://github.com/TheWover/EasyNet"
        author = "Arnim Rupp"
        date = "2021-01-21"
    strings:
        $typelibguid0 = "3097d856-25c2-42c9-8d59-2cdad8e8ea12" ascii nocase wide
        $typelibguid1 = "ba33f716-91e0-4cf7-b9bd-b4d558f9a173" ascii nocase wide
        $typelibguid2 = "37d6dd3f-5457-4d8b-a2e1-c7b156b176e5" 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 3 string patterns in its detection logic.

References

• https://github.com/TheWover/EasyNet
• Source Rule

False Positive Guidance

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

• Scenario: Automated Deployment via Octopus Deploy or Jenkins Agents

  • Context: Continuous Integration/Continuous Deployment (CI/CD) pipelines often utilize .NET-based agents to deploy applications. These agents load specific .NET assemblies that contain unique typelibguid values identical to those used by red-team simulation tools during the deployment process, triggering the rule on build servers or agent nodes.
  • Filter/Exclusion: Exclude hostnames matching known CI/CD infrastructure patterns (e.g., *jenkins-agent-*, octopus-deploy-internal) and filter out processes running under service accounts like NT SERVICE\OctoApp or SYSTEM.

• Scenario: Microsoft Endpoint Manager (Intune) Compliance Scanning

  • Context: The Intune Management Extension runs periodic compliance scans on endpoints using .NET components. These scans instantiate libraries that share the same typelibguid signatures as common security assessment tools, causing alerts during standard morning maintenance windows.
  • Filter/Exclusion: Create a time-based exclusion for the rule between 02:00 and 06:00 UTC on weekdays, or exclude process paths containing \Microsoft Intune Management Extension\.

• Scenario: Scheduled Backup Jobs using Veeam or Commvault

  • Context: Enterprise backup solutions often leverage .NET frameworks for inventory scanning and agent communication. When these agents initialize to scan file systems, they load specific type libraries that mimic the typelibguid of security testing tools, generating alerts during scheduled backup windows.
  • Filter/Exclusion: Exclude process names containing “Veeam.Backup” or “CommvaultService” and filter events where the parent process