22 COPublished by the ieee COmPuter and reliability sOCieties ■ 1540-7993/09/$26.00 © 2009 ieee ■ July/august 2009 Completely Automated Public Turing Tests to Tell Computers and Humans Apart (CAPTCHAs) are now an almost standard security mechanisms for defending against undesirable and malicious bot programs on the Internet (especially those bots that can sign up for thousands of accounts a min...

Phishing is an attempt by an individual or a group to get personal confidential information such as passwords, credit card information from unsuspecting victims for identity theft, financial gain and other fraudulent activities. Fake websites which appear very similar to the original ones are being hosted to achieve this. In this paper we have proposed a new approach named as "Countering Phishi...

Completely Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a HIP (Human interactive Proof) system. CAPTCHAs are used to improve the security of Internet based applications in order to ensure that a web based application which is intended to be used by a human being is not maliciously used by Artificially Intelligent programs called bots. As the current CAPTCHA metho...

With data theft and computer break-ins becoming increasingly common, there is a great need for secondary authentication to reduce automated attacks while posing a minimal hindrance to legitimate users. CAPTCHA is one of the possible ways to classify human users and automated scripts. Though textbased CAPTCHAs are used inmany applications, they pose a challenge due to language dependency. In thi...

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 ...

Simple, universally applicable strategies can help any captchaprotected system resist automated attacks and can improve the ability of administrators to detect attacks. The strategies discussed here cause an exponential increase in the difficulty faced by automated attackers, while only increasing the inconvenience for human users in an approximately linear manner. These strategies are characte...

Many CAPTCHA proposals have shortcomings in their design or implementation that make themmuch weaker than intended. In this paper we study Captcha2, a commercial algorithm, as a means of showing typical flaws that make many CAPTCHAs prone to successful low-cost attacks. The attack we present makes no use of any AI techniques, not affecting the resilience of the original AI problem this CAPTCHA ...

CAPTCHAs are a widely deployed mechanism to distinguish a legitimate human user from a computerized program trying to abuse online services. Attackers, however, have devised a clever and an economical way to bypass the security provided by CAPTCHAs by simply relaying CAPTCHA challenges to remote human-solvers. Most existing varieties of CAPTCHAs are completely vulnerable to such relay attacks, ...

This work focuses on development of an alternative aural CAPTCHA technology based on a speech transcription task. The principal goals are (1) to provide a better quality of service for visually impaired web users who currently have few alternatives for accessing web services protected by CAPTCHAs based on visual perception tasks, (2) as a side effect of CAPTCHA use, collect meaning data, such a...

Completely Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a HIP (Human interactive Proof) system. CAPTCHAs are used to improve the security of Internet based applications in order to ensure that a web based application which is intended to be used by a human being is not maliciously used by Artificially Intelligent programs called bots. As the current CAPTCHA metho...