Dynamic Image Based CAPTCHA

Web security has become a critical and challenging issue due to the growth of Internet. BOT is one of the most malicious threats to the web services. It runs automated tasks over the internet and creates problem. One solution for securing web from BOT is to develop CAPTCHA. CAPTCHA is acronym for Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHA may be textual or image based CAPTCHA. In this paper dynamic image based three tier CAPTCHA system is proposed. The layers are 1) Image access layer2) Image processing layer and 3) Presentation layer. The proposed system makes cracking a difficult task for BOT, but at the same time it is easier for human to perceive it. In this paper strengths and weaknesses of available image based CAPTCHAs and working steps of proposed algorithm have been discussed. It is observed that the probability of a BOT hacking the proposed prototype system is considerably low.