Dynamic CAPTCHA

Registration Websites use CAPTCHA (completely automated public turing test to tell computers and human apart) systems to prevent the bot programs from wasting their resources. But sometimes the CAPTCHA test is difficult for human users to pass because the users have different ages, languages, etc. In this paper we propose a solution for this problem. The registration system can select a kind of CAPTCHA system among different available CAPTCHA systems regarding to the user's needs such as user language and disabilities. For example if the user has non-English language, the system chooses a CAPTCHA method which does not need English language knowledge.