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...

Captcha is a popular real user detection or autobot/robot rejection technique used in websites for Desktops. Captcha is also in use in some of the mobile websites. Captcha are difficult to read on the smartphone and portable computer screens. Users stuck in zooming in/zooming out while reading and filling the captcha and other required fields. Old aged users feel it more difficult to view and t...

Accessibility concerns compound the already-considerable difficulties of building systems that provide usable privacy and security. In addition to facing common concerns regarding the semantics of privacy and security tools, people with disabilities face accessibility obstacles, such as the inaccessibility of CAPTCHAs, phishing toolbars, verification images, and other displays that rely upon vi...

The research presented in this thesis aims to extend the capabilities of human interaction proofs in order to improve security in web applications and services. The research focuses on developing a more robust and efficient Completely Automated Public Turing test to tell Computers and Human Apart (CAPTCHA) to increase the gap between human recognition and machine recognition. Two main novel app...

The use of colour in user interfaces is extensive. It is typically a usability issue, and has rarely caused any security concerns. In this article, we show that the use of colours in the design of CAPTCHA, a standard security technology that has found widespread applications in commercial websites, can have interesting but critical implications on both security and usability. © 2010 University ...

The effectiveness of CAPTCHA challenges largely depends on being simultaneously easier to solve for humans and harder to solve for bots. In this work we argue that it is possible to enhance the effectiveness of audio CAPTCHA challenges by adapting the challenge to the users’ characteristics. We propose a method for achieving this adaptation while protecting users’ privacy. Moreover, our approac...

CAPTCHA is a technology which has its base in a test called the Turing Test. Alan Turing, proposed this test as a way to examine whether or not machines can think or appear to think like humans. The main purpose of a CAPTCHA is to block form submissions from spam botsthat is automated scripts. Various types of CAPTCHAs are used, which mostly requires users to enter the strings of characters tha...

-We are in the era of internet and depend on it for every necessary requirement. It is the tendency of the some human to have destructive approach rather than having constructive approach. Among the abuse and misuse of internet, the distributed denial of service attack (DDOS) is the most hectic one. People have carried out various method of mitigation using the CAPTCHA (Completely Automated Pub...

Every user appreciates the security of their data irrespective of its sensitivity. At the same time, user does not want to be held up with the legacy systems, which may be strongly secured but not with fantasy. Network travelled many phases of its own such as internet, intranet, wireless network, sensor network, Ad-hoc network, Mobile network, Blue-tooth, Cloud and IoT, the most popular techniq...