In this paper we present a new CAPTCHA system (Completely Automated Turing Test To Tell Computers and Humans Apart). The proposal of SemCAPTCHA is motivated by an increasing number of broken OCR-based CAPTCHA systems and it is based not only on text recognition but also on text understanding. We describe both, the user’s and the system’s perspective of SemCAPTCHA and compare it with some curren...

CAPTCHA stands for “Completely Automated Public Turing test to tell Computers and Humans Apart” and has received much attention since it first began appearing on websites. It requires the deciphering of distorted texts, mostly in English which is something that computers still cannot do well. It is also helpful in preventing the abuse of online services. The current text-based CAPTCHA requires ...

A recent study has found that malicious bots generated nearly a quarter of overall website traffic in 2019 [100]. These perform activities such as price and content scraping, account creation takeover, credit card fraud, denial service, etc. Thus, they represent serious threat to all businesses general, but are especially troublesome for e-commerce, travel financial services. One the most commo...

CAPTCHA is now commonly used as standard security technology to tell computers and humans apart. The most widely deployed CAPTCHAs are text-based schemes. In this paper, we document how we have broken such a text-based scheme which uses the “connecting characters together (CCT)” principle. CAPTCHAs of this type can be classified into three types: CAPTCHA with overlap but no noise arcs; CAPTCHA ...

The Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is used to believe that a human is using the web service [1]. For the online services which are been provided in web services is been abused by automated bots over the internet. So CAPTCHA is used as a protection from these malicious programs for web security. But the bots are intelligent enough to break th...

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...

Purpose In this work we argue that it is possible to address discrimination issues that naturally arise in contemporary audio CAPTCHA challenges and potentially enhance the effectiveness of audio CAPTCHA systems by adapting the challenges to the user characteristics. Design/methodology/approach We design a prototype, called PrivCAPTCHA, to offer privacy-preserving, user-centric CAPTCHA challeng...

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...