Cloudflare Workers for Ad Traffic Filtering: A Serverless Approach

Cloudflare Workers sit at the edge, making them perfect for filtering ad traffic before it reaches your server.

Why Edge-Based Filtering?

Latency: <5ms added to request
Scale: Handles millions of requests
Cost: Pay-per-request pricing
No infrastructure: Serverless

Implementation

export default {
    async fetch(request, env) {
        const ip = request.headers.get('CF-Connecting-IP');
        const ja3 = request.headers.get('CF-JA3');
        const country = request.headers.get('CF-IPCountry');

        // Layer 1: IP reputation
        const ipScore = await checkIPReputation(ip, env);
        if (ipScore < 20) {
            return new Response('', { status: 403 });
        }

        // Layer 2: TLS fingerprint
        if (KNOWN_BOT_JA3.includes(ja3)) {
            return serveSafePage(request);
        }

        // Layer 3: Pass to origin with scoring headers
        const modifiedRequest = new Request(request, {
            headers: {
                ...Object.fromEntries(request.headers),
                'X-Bot-Score': ipScore.toString(),
                'X-TLS-Risk': ja3Risk.toString()
            }
        });

        return fetch(modifiedRequest);
    }
};