john_crack · Kali MCP: Risk & Policy

WHAT IT DOES

What john_crack does on Kali

AI agents invoke john_crack to trigger actions in Kali. 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 john_crack needs a policy

John the Ripper is a well-known password cracking tool. Even though the description is empty, the tool name combined with the server context (Kali Linux pentest server with 'password attacks' capability) makes it highly likely this tool executes password cracking operations. Password cracking can compromise authentication systems at scale, warranting critical severity.

From the tool's definition Tool name 'john_crack' strongly implies John the Ripper password cracking; server description mentions 'password attacks' among 90+ penetration testing tools

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

john_crack Rate-limited

john_crack 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": {
    "john_crack": {
      "limits": [
        {
          "counter": "john_crack_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 Kali, so you can run agents against it safely.

FAQ

Questions about john_crack

What does the john_crack tool do? +

john_crack. It is categorised as a Execute tool in the Kali MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on john_crack? +

Register the Kali MCP server in PolicyLayer and add a rule for john_crack: 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 Kali. Nothing to install.

What risk level is john_crack? +

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

Can I rate-limit john_crack? +

Yes. Add a rate_limit block to the john_crack 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 john_crack completely? +

Set action: deny in the PolicyLayer policy for john_crack. 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 john_crack? +

john_crack is provided by the Kali MCP server (pentestt00ls/kali-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.