Reverse Turing tests, or CAPTCHAs, have become an ubiquitous defense used to protect open Web resources from being exploited at scale. An effective CAPTCHA resists existing mechan...
Marti Motoyama, Kirill Levchenko, Chris Kanich, Da...
A CAPTCHA is a program that generates challenges that are easy to solve for humans but difficult to solve for computers. The most common CAPTCHAs today are text-based ones where a ...
Paul Baecher, Marc Fischlin, Lior Gordon, Robert L...
CAPTCHAs are computer-generated tests that humans can pass but current computer systems cannot. CAPTCHAs provide a method for automatically distinguishing a human from a computer ...
—Captchas are designed to be easy for humans but hard for machines. However, most recent research has focused only on making them hard for machines. In this paper, we present wha...
Elie Bursztein, Steven Bethard, Celine Fabry, John...
We introduce captcha, an automated test that humans can pass, but current computer programs can’t pass: any program that has high success over a captcha can be used to solve an u...
Luis von Ahn, Manuel Blum, Nicholas J. Hopper, Joh...
CAPTCHAs are tests that distinguish humans from software robots in an online environment [3, 14, 7]. We propose and implement three CAPTCHAs based on naming images, distinguishing ...
Abstract. Current CAPTCHAs require users to solve objective questions such as text recognition or image recognition. We propose a class of CAPTCHAs based on collaborative filterin...
We show how to convert regular keyboard-entry CAPTCHAs into clickable CAPTCHAs. The goal of this conversion is to simplify and speed-up the entry of the CAPTCHA solution, to minim...
Richard Chow, Philippe Golle, Markus Jakobsson, Lu...
CAPTCHAs are automated Turing tests used to determine if the end-user is human and not an automated program. Users are asked to read and answer Visual CAPTCHAs, which often appear...