期刊名称：International Journal of Computer Science and Information Technologies
电子版ISSN：0975-9646
出版年度：2014
卷号：5
期号：2
页码：2242-2245
出版社：TechScience Publications
摘要：CAPTCHA is an acronym for Completely Automated Public Turning Test to tell Computers and Humans Apart [1]. CAPTCHA is basically used as a protection from these malicious programs like Bot. Now a day’s for web security we are using different type of captcha. In this paper we describe all type of captcha and also describe their drawbacks all type of captcha. We also describe application of captcha. And review paper of different types of Captcha.
