Express (Node.js)

Express is the backbone of the Node.js ecosystem. To protect your API routes or web application, you can implement ProxyTracer as a global or route-specific middleware.

The Middleware

This implementation extracts the client IP (handling X-Forwarded-For headers if you are behind a reverse proxy like NGINX or AWS ALB), queries ProxyTracer using native fetch, and immediately drops the connection with a 403 Forbidden if a threat is detected.


const express = require('express');
const app = express();
 
// Trust the reverse proxy to ensure req.ip is accurate
app.set('trust proxy', true); 
 
const proxyTracerMiddleware = async (req, res, next) => {
  // 1. Extract the IP
  // Express handles 'trust proxy' automatically, but we can fallback just in case
  const ip = req.headers['x-forwarded-for']?.split(',')[0].trim() || req.ip;
 
  // Pass through if local development
  if (!ip || ip === '::1' || ip === '127.0.0.1') {
    return next();
  }
 
  try {
    // 2. Query ProxyTracer API (Node 18+ supports native fetch)
    const ptResponse = await fetch(`https://api.proxytracer.com/v1/check/${ip}`, {
      method: 'GET',
      headers: {
        'Authorization': `Bearer ${process.env.PROXYTRACER_API_KEY}`
      }
    });
 
    if (ptResponse.ok) {
      const data = await ptResponse.json();
 
      // 3. Drop the connection if a proxy/VPN is detected
      if (data.proxy === true) {
        return res.status(403).json({
          error: "Access Denied: VPN or Proxy detected."
        });
      }
    }
  } catch (error) {
    // Fail open: If the API is unreachable, allow traffic to ensure uptime
    console.error('ProxyTracer API Error:', error);
  }
 
  // 4. Traffic is clean, proceed to the controller
  next();
};
 
// Apply globally to all routes
app.use(proxyTracerMiddleware);
 
// Or apply strictly to sensitive routes
// app.post('/api/checkout', proxyTracerMiddleware, checkoutController);