CAPTCHA is an important technology to prevent auto-script attack. Currently most of the CAPTCHA systems are text based, which firstly distort, rotate different characters and then use some obfuscation, aiming to make the text difficult to be recognized by autoscript while still can be learnt easily by real users. However, such kind of CAPTCHA schema either too simple, which can be attacked easi...

CAPTCHAs have become a standard security mechanism that are used to deter automated abuse of online services intended for humans. However, many existing CAPTCHA schemes to date have been successfully broken. As such, a number of CAPTCHA developers have explored alternative methods of designing CAPTCHAs. 3D CAPTCHAs is a design alternative that has been proposed to overcome the limitations of tr...

INCORPORATING PRIVACY AND SECURITY FEATURES IN AN OPEN SOURCE SEARCH ENGINE The aim of this project was to explore and implement various privacy and security features in an open-source search engine and enhance the security and privacy capabilities of Yioop. Yioop, an open-source PHP search engine based on GPLv3 license, is designed and developed by Dr. Chris Pollett. We have enabled a crawl, s...

Many websites utilise CAPTCHA (Completely Automatic Public Turing tests to tell Computers and Humans Apart) schemes as human interaction proofs to grant access to their services only to people rather than spam bots. In this paper, we examine the security of six widely used types of CAPTCHA and present novel attacks against all of them, achieving success rates of up to 88%. We made improvements ...

Video CAPTCHA improves the usability while reducing the attack success rate compared to a conventional text-based CAPTCHA. However, it remains vulnerable to OCR attacks. Thus, we proposed to use inpainting algorithms to remove the contained text in the video frames, so that the OCR success rate can be reduced without introducing unwanted artifacts that displease the endusers. We implemented Ber...

CAPTCHAs is Turing test are used to distinguish whether a user is a human or a computer. Till today huge number of CAPTCHA schema have been suggest or put forth and applied on miscellaneous websites to secure online services (SOS) from automated decaptcha programs. So development of a good CAPTCHA scheme that is both secure by automated recognition and human usable is an important research prob...

The increasing use of smart phones, tablets, and other mobile devices poses a significant challenge in providing effective online security. CAPTCHAs, tests for distinguishing human and computer users, have traditionally been popular; however, they face particular difficulties in a modern mobile environment because most of them rely on keyboard input and have language dependencies. This paper pr...

With the growing and prevalent usage of Internet, threat for the service providers has arisen. One of the most important aspects of modern security concerns is to deal with users that are computer programs or bots. These programs pretend to be human users and exploit servers by submitting data automatically, thereby, hindering the services of the server. Security mechanism dealing with such att...

CAPTCHAs are essentially challenge-response tests that are used to distinguish whether a user is a human or a computer. To date, numerous CAPTCHA schemes have been proposed and deployed on various websites to secure online services from abuse by automated programs. However, many of these CAPTCHAs have been found to suffer from design flaws that can be exploited to break the CAPTCHA. Hence, the ...

DESIGNING A FACE DETECTION CAPTCHA Adam C. Day Completely Automated Tests for Telling Computers and Humans Apart (CAPTCHAs) are quickly becoming a standard for security in every online interface that could be the subject to spam or other exploitation. The majority of today's CAPTCHA technologies rely on text-based images, which present the user with a string of distorted characters and asks the...