CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) - is a security test designed to distinguish between human users and visitors. The main job of this web form is to protect against spam and stop automatons (called bots) from entering any data into a website. Bots are programmed to perform specific tasks, meaning that they follow instructions without a human having to run them each time manually. Traditional captchas often mimic or replace the behavior of a human user - and if used viciously, they can have a devastating effect on any website they attack.