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mcpwall

behrensd/mcp-firewall

A transparent stdio proxy that sits between your AI client and any MCP server, enforcing YAML-defined security policies on every JSON-RPC call. It blocks dangerous tool invocations (SSH key access, `rm -rf`, pipe-to-shell), scans arguments and responses for leaked secrets using regex and entropy analysis, and logs everything to a JSON Lines audit trail. Ships with sensible defaults but supports custom rules for path restrictions, command patterns, and secret detection. Works with Docker MCP Toolkit, Claude Code, Cursor, and any stdio-based MCP server. Think iptables for your AI toolchain: no LLM decisions, no cloud calls, just deterministic rules that stop your assistant from reading `.env` files or exfiltrating API keys before the request hits the filesystem server.

tools
2
transport
STDIO
last updated
Feb 17, 2026
View on GitHub

Tools

2 tools

Public tool metadata for what this MCP can expose to an agent.

execute_safelyFIREWALL: Describe ANY crypto action and I'll check if it's safe. Call this BEFORE every transaction. I check all addresses involved for scams, honeypots, and phishing. Returns GO or BLOCK. Examples: - "Swap 0.1 ETH for 0x4ed4...ed on base" - "Approve 0x1234... to spend my USD...1 params

FIREWALL: Describe ANY crypto action and I'll check if it's safe. Call this BEFORE every transaction. I check all addresses involved for scams, honeypots, and phishing. Returns GO or BLOCK. Examples: - "Swap 0.1 ETH for 0x4ed4...ed on base" - "Approve 0x1234... to spend my USD...

Parameters* required
action_descriptionstring
firewall_statusCheck firewall status and what it protects against.

Check firewall status and what it protects against.

No parameter schema in public metadata yet.

Sponsors

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Readme

mcpwall

npm version CI Node.js License: Apache-2.0

iptables for MCP. Blocks dangerous tool calls, scans for secret leakage, logs everything. No AI, no cloud, pure rules.

Sits between your AI coding tool (Claude Code, Cursor, Windsurf) and MCP servers, intercepting every JSON-RPC message and enforcing YAML-defined policies.

mcpwall demo — blocking SSH key theft, pipe-to-shell, and secret leakage

mcpwall check — test any tool call against your rules without running the proxy

Why

View the full README on GitHub

Details

Repository
github.com/behrensd/mcp-firewall
Category
Security & Pentesting
Package
mcpwall
Transport
STDIO
Registry
MCP registry, active

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