A click bot is software built to click advertisements automatically. Bots are responsible for the majority of large-scale click fraud, and they have evolved far beyond the obvious crawlers that Google's filters catch.
Basic programs (curl, Python requests) that fetch an ad URL repeatedly. They send no real browser signals, so they're easy to identify — most are caught by Google's own invalid-click filters.
Real Chrome or Firefox engines running without a screen, automated by tools like Selenium or Puppeteer. They execute JavaScript, load pages fully and look far more human. Their tell-tale signs — automation flags in the user-agent, zero interactions, instant bounces — only show up in on-page behavioural data.
The most damaging form: headless browsers distributed across thousands of datacenter and residential proxy IPs, rotating every few clicks. Blocking individual IPs is useless — by the time you block one, the bot has moved to the next.
Google evaluates clicks mainly with auction-side data: IP reputation, click patterns and account history. It never sees what happens on your landing page. A headless browser that loads your page, waits two seconds and leaves looks — to Google — like an uninterested human. To behavioural tracking, the missing scroll, missing interactions and automation fingerprints are unmistakable.