AI agents invoke start_ncat_listener to trigger actions in Pentester-MCP. 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.
This tool initiates a network listener, which is an active operation that establishes listening network sockets and can interact with external systems. The effects depend heavily on how an AI agent configures it (port, protocol, handler) and what connects to it, making it an Execute class tool rather than Read (no passive query) or Write (network listeners have active, runtime effects beyond simple data…
From the tool's definition Tool name 'start_ncat_listener' indicates launching Ncat (network utility) in listener mode. Ncat is a networking tool capable of setting up TCP/UDP listeners that can execute commands, receive reverse shells, or relay network traffic.
Documented attack patterns abuse exactly the kind of access start_ncat_listener gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pentester-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for start_ncat_listener:
{
"version": "1",
"default": "deny",
"tools": {
"start_ncat_listener": {
"limits": [
{
"counter": "start_ncat_listener_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}start_ncat_listener 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.
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start_ncat_listener. It is categorised as a Execute tool in the Pentester-MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Pentester- MCP server in PolicyLayer and add a rule for start_ncat_listener: 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 Pentester-MCP. Nothing to install.
start_ncat_listener is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the start_ncat_listener 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.
Set action: deny in the PolicyLayer policy for start_ncat_listener. 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.
start_ncat_listener is provided by the Pentester- MCP server (halilkirazkaya/pentester-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Pentester-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
337 Pentester-MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.