Analysis of Different Text Based Captcha Methods

CAPTCHA stands for completely automated public turing test to tell computers and humans apart. The primary duty of Captcha is to separate humans and bots. Captcha generates a challenge response test and direct the users to perform a simple task. It is easy for the humans to complete the task, whereas it is difficult for the bot programs.Thus Captcha becomes a standard security mechanism in all the websites and web applications to prevent Internet Bots from unauthorised access.