A Review on Various Implemented CAPTCHA in the Field of Web Security

Abstract

CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a process of identifying whether user is human or robot. It is very important to know the user end because security can be breach. There are different CAPTCHA problems accessible like twisted string, image recognition, math and gaming CAPTCHA. Game based problem is intuitive and profoundly got as contrast with the other CAPTCHA. In this sort of CAPTCHA client needs to tackle an AI problem either by drag and drop technique or click based, contingent upon the game. The paper is expected to audit different carried out CAPTCHA and analyze their shortcoming and security boundaries. A large number of the CAPTCHAs are based on click based strategies where client needs to recognize the photos according to its appearance and snap in like manner. However, this sort of CAPTCHA can be mediated by image processing like object classifier. Dragging an item to the objective region is a successful way however it must be performed or tackled by a scholarly problem. On the off chance that dragging an item to the objective region by object acknowledgment, framework might get broken by relay attacks. Keywords: CAPTCHA, Gaming CAPTCHA, Picture Recognition, Web Security, Image Processing, Relay Attacks.