Detects .NET red/black-team tools via name

Hunt Hypothesis

This hunt hypothesis identifies the execution of known .NET-based Red and Blue team utility names to distinguish legitimate security operations from potential adversary tooling that mimics these signatures. Proactively hunting for this behavior in Azure Sentinel allows the SOC team to validate authorized activities while uncovering stealthy attacks where adversaries leverage familiar .NET tools to evade standard detection thresholds.

YARA Rule

rule HKTL_NET_NAME_RAT_NjRat_0_7d_modded_source_code {
    meta:
        description = "Detects .NET red/black-team tools via name"
        reference = "https://github.com/AliBawazeEer/RAT-NjRat-0.7d-modded-source-code"
        author = "Arnim Rupp"
        date = "2021-01-22"
    strings:
        $name = "RAT-NjRat-0.7d-modded-source-code" ascii wide
        $compile = "AssemblyTitle" ascii wide
    condition:
        (uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550) and all 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 2 string patterns in its detection logic.

References

False Positive Guidance

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

Scenario: Automated Vulnerability Scanning via PowerShell
- Context: The enterprise uses a scheduled task to run Invoke-WebRequest or custom scripts utilizing the System.Management.Automation assembly to perform internal vulnerability scans. These scripts often invoke .NET assemblies with names resembling security tools (e.g., VulnScan.Core.dll).
- Filter/Exclusion: Create an exclusion based on the Parent Process Name (Taskeng.exe or svchost.exe) and restrict detection to specific User Contexts (e.g., exclude NT SERVICE\TaskScheduler or dedicated service accounts like svc-vulnscan).
Scenario: Microsoft Defender for Endpoint Real-Time Protection
- Context: The native Microsoft Defender engine frequently loads .NET-based components such as MpCmdRun.exe or MsMpEng.dll which contain internal tooling libraries. These components often match the naming convention of external red-team tools (e.g., containing “Cobalt” or “Sharp” in their assembly names) during routine definition updates.
- Filter/Exclusion: Exclude processes where the Image Path contains Program Files\Windows Defender and filter out events where the File Hash matches known Microsoft-signed binaries (verify via a hash allow-list).
Scenario: Enterprise Configuration Management (SCCM/MEM)
- Context: System Center Configuration Manager (SCCM) or Microsoft Endpoint Manager executes deployment jobs using .NET wrappers. When deploying software updates, the ccmsetup.exe process spawns child processes like AppDeploymentTool.dll, which mimics the naming structure of red-team execution tools used in penetration testing.
- **Filter/Ex