… 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 …

… compare different types of CAPTCHA and its alternatives to … that have been conducted on
CAPTCHA and its alternative … 2, the underlying concepts of CAPTCHA, its definitions as well …

… We present a new CAPTCHA which is based on identifying … The main advantages of our
CAPTCHA technique over the … for CAPTCHA generation beyond character obfuscation. This …

… and Humans Apart" (CAPTCHA) is a … CAPTCHA mechanism was conducted in order to
investigate several aspects that affect end-user perceptions related to the quality of CAPTCHA. A …

… than 90% on the latest version of this Microsoft CAPTCHA (as deployed in the summer of
2007)1. For convenience, we will refer to this CAPTCHA as the MSN scheme in this paper. With …

… of the CAPTCHA. This paper examines recent research on various CAPTCHA methods
and their categories. Moreover it discusses the weakness and strength of these types. …

… The remainder of this paper is organized as follows: Section 2 reviews CAPTCHA design
and provides a qualitative history and overview of the CAPTCHAsolving ecosystem. Next, in …

… when solving a CAPTCHA. Thus, if the classifier is able to solve a CAPTCHA correctly we
can … Of course, if the CAPTCHA is not solved we don’t have that information, but we will show …

… , we provide a discussion on the current state-of-the-art of CAPTCHA, highlighting the
CAPTCHA evolution and the limitations of each CAPTCHA design from different standpoints. …

We propose IMAGINATION (IMAge Generation for INternet AuthenticaTION), a system for
the generation of attack-resistant, user-friendly, image-based CAPTCHAs. In our system, we …

… how those flaws can be used to completely solve this CAPTCHA using a low-cost attack. This
… other CAPTCHA proposals. We conclude with some tips for enhancing this CAPTCHA that …

… in previous sections, existing CAPTCHA types, attack types and CAPTCHA vulnerabilities
are summarized. We conclude by proposing a new CAPTCHA scheme to address these …

… on the development of CAPTCHA technologies for human … CAPTCHA survey, this review
discusses the CAPTCHA … current CAPTCHA are both reviewed. Besides, recent emerging …

… Unfortunately, many CAPTCHA have been already broken by bots and some CAPTCHA
are difficult to read by human. In this paper, a new CAPTCHA method called 3D CAPTCHA is …

… One of the CAPTCHA methods is Collage CAPTCHA. In this method some shapes are … of
Collage CAPTCHA method [2]. In this section, after describing the original Collage CAPTCHA …

… and selects the difficulty of the captcha that will be returned. … We also apply our attack to the
Facebook image captcha and … we will refer to this type of captcha as the checkbox captcha. …

… In this paper, we introduce DeepCAPTCHA, a new and secure CAPTCHA scheme based …
We show that plain adversarial noise is insufficient to achieve secure CAPTCHA schemes, …

… A typical CAPTCHA is an image containing several distorted characters that appears at the
bottom of Web registration forms. Users are asked to type the wavy characters to “prove” they …

We present the malicious CAPTCHA attack, allowing a rogue website to trick users into
unknowingly disclosing their private information. The rogue site displays the private information …

In this paper we explore object recognition in clutter. We test our object recognition
techniques on Gimpy and EZ-Gimpy, examples of visual CAPTCHAs. A CAPTCHA ("Completely …