nmap_custom_scan · Nmap MCP Server MCP: Risk & Policy

WHAT IT DOES

What nmap_custom_scan does on Nmap MCP Server

AI agents invoke nmap_custom_scan to trigger actions in Nmap MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why nmap_custom_scan needs a policy

This tool executes Nmap network scanning with fully custom, user-defined options. Since the user controls the flags, this could enable aggressive scanning, exploitation scripts, or scanning unauthorized targets. Network scanning is an active operation with external side effects (sending packets to arbitrary hosts), and unrestricted option control raises the blast radius significantly.

From the tool's definition 'Perform custom Nmap scan with user-defined options' — arbitrary user-defined options passed to Nmap

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

nmap_custom_scan Rate-limited

nmap_custom_scan stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "nmap_custom_scan": {
      "limits": [
        {
          "counter": "nmap_custom_scan_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Nmap MCP Server, so you can run agents against it safely.

FAQ

Questions about nmap_custom_scan

What does the nmap_custom_scan tool do? +

Perform custom Nmap scan with user-defined options. It is categorised as a Execute tool in the Nmap MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on nmap_custom_scan? +

Register the Nmap MCP Server MCP server in PolicyLayer and add a rule for nmap_custom_scan: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Nmap MCP Server. Nothing to install.

What risk level is nmap_custom_scan? +

nmap_custom_scan is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit nmap_custom_scan? +

Yes. Add a rate_limit block to the nmap_custom_scan rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block nmap_custom_scan completely? +

Set action: deny in the PolicyLayer policy for nmap_custom_scan. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides nmap_custom_scan? +

nmap_custom_scan is provided by the Nmap MCP Server MCP server (mohdhaji87/nmap-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.