I Lost $15K to Bot Traffic in One Month — Here's What I Built to Stop It

This is a real story. Last year I was running native ad campaigns spending $500/day. My ROAS looked great on paper — until I dug into the data. The Discovery I noticed something weird in my analytics: 73% bounce rate on what should be a high-intent landing page Average time on page: 2.3 seconds Conversion rate dropped from 4.2% to 1.1% over 3 weeks I ran a simple test — added mouse movement tracking to my landing page. The results were shocking: over 40% of my "visitors" had zero mouse movement events. No mouse movement = no human = bot. The $15K Math Daily spend: $500 Bot traffic: ~40% Wasted: $200/day × 75 days = $15,000 What I Built I built a three-layer detection system: Layer 1: IP Intelligence def score_ip(ip): score = 100 if is_datacenter(ip): score -= 40 if is_known_proxy(ip): score -= 30 if request_frequency(ip) > 10: score -= 20 return max(0, score) Layer 2: Browser Fingerprint Validation Canvas, WebGL, AudioContext fingerprints vs known bot signatures. Layer 3: Behavioral