The massive and automated access to Web resources through robots has made it essential for Web service providers to make some conclusion about whether a user is human or robot. A Human Interaction Proof (HIP) like Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) offers a way to make such a distinction. CAPTCHA is essentially a modern implementation of Turing test, which carries out its job through a particular text based, image based or audio based challenge response system. In this paper we present a new image based CAPTCHA technique. Properties of the proposed technique offer all of the benefits of image based CAPTCHAs; grant an improved security control over the usual text based techniques and at the same time improve the user-friendliness of the Web page. Further, the paper briefly reviews various other existing CAPTCHA techniques.
Shah, Nisar A. and Banday, M. Tariq, " Drag and Drop Image CAPTCHA " (2010). All Sprouts Content. 250.