nBinderv40

Hunt Hypothesis

This hypothesis targets the execution of the nBinder v4.0 tool, a lightweight Windows binary often used by adversaries to establish persistence or execute payloads without requiring a full .NET runtime. Proactively hunting for this specific YARA signature in Azure Sentinel helps identify low-severity, fileless or minimal-footprint implantations that may slip past traditional endpoint detections due to their small size and common naming conventions.

YARA Rule

rule nBinderv40
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 5C 6E 62 34 5F 74 6D 70 5F 30 31 33 32 34 35 34 33 35 30 5C 00 00 00 00 00 00 00 00 00 E9 55 43 4C FF 01 1A 00 00 00 00 96 30 07 77 2C 61 0E EE BA 51 09 99 19 C4 6D 07 8F F4 6A 70 35 A5 63 E9 A3 95 64 9E 32 88 DB 0E A4 B8 DC 79 }

condition:
		$a0
}

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.

• Source Rule

False Positive Guidance

• Scenario: A system administrator manually runs the nbinderv40 binary (or its associated installer) to update the network binding driver on a domain controller or file server as part of a scheduled maintenance window.

  • Filter/Exclusion: Exclude executions where the parent process is explorer.exe or cmd.exe initiated by an interactive user session, specifically when the file path resides in a known administrative tools directory (e.g., C:\AdminTools\ or C:\Temp\Updates\) and the command line contains arguments like /install or /update.

• Scenario: An enterprise endpoint management agent (such as SCCM, Intune, or Ansible) pushes the nbinderv40 update package to a fleet of Windows servers, causing the binary to execute from a temporary network share or staging folder during the deployment cycle.

  • Filter/Exclusion: Exclude executions where the parent process is a known management agent service (e.g., ccmexec.exe, IntuneAgent.exe, or ansible-service-runner.exe) and the file path includes a staging directory pattern like \Temp\, \Staging\, or \Deployment\.

• Scenario: A developer or QA engineer runs the nbinderv40 utility in a local development environment or test lab to validate network configuration changes before promoting the build to production.

  • Filter/Exclusion: Exclude executions on hosts tagged with a “Dev” or “Test” environment label in the asset inventory, or exclude paths that explicitly contain dev, test, or lab in the directory structure (e.g., C:\DevProjects\network-tools\).

• Scenario: A third-party backup or monitoring solution (e.g., Veeam, SolarWinds) bundles the nbinderv40 driver as a dependency for