CAPTCHAs exploit the gap in the ability between a human and a machine to understand the semantics of specific multimedia content, with vast applications in computer security. In this paper we compare two techniques in automated CAPTCHA solving for text-based CAPTCHA schemes, i.e., classification based on the Vector Space Model (VSM) versus a popular Optical Character Recognition (OCR) engine. F...

This paper discusses and demonstrates the interplay between system security and user interface convenience in CAPTCHA design, and in particular, mobile device CAPTCHA design. A CAPTCHA is a computer-based security test used to distinguish human users from artificial users, preventing automated abuse of networked resources. As mobile network services improve, we can anticipate that future mobile...

Currently, it is unavoidable of typing CAPTCHA (Completely Automated Public Turing test to tell Computer and Human Apart) before accessing to the Internet. This technique mostly can distinguish bots from human being. Thus, the system is protected from any unwanted persons or programs. There are various researches proposed several of CAPTCHA techniques to protect bots. These are such as Text-bas...

This paper proposes JACI (Just Another CAPTCHA Implementation). JACI is an image-based CAPTCHA technology that requires users to match like images with their partner image in order to pass the test. JACI is not dependant on keyboard interaction which aids some forms of accessibility and does not require internationalisation. Interaction is controlled with a pointing device such as a mouse; as e...

DESIGNING A FACE DETECTION CAPTCHA Adam C. Day Completely Automated Tests for Telling Computers and Humans Apart (CAPTCHAs) are quickly becoming a standard for security in every online interface that could be the subject to spam or other exploitation. The majority of today's CAPTCHA technologies rely on text-based images, which present the user with a string of distorted characters and asks the...

The massive and automated access to Web resources through robots has made it essential for Web service providers to make some conclusion about whether the ”user” is a human or a robot. A Human Interaction Proof (HIP) like Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) offers a way to make such a distinction. CAPTCHA is a reverse Turing test used by Web serv...

Video CAPTCHA improves the usability while reducing the attack success rate compared to a conventional text-based CAPTCHA. However, it remains vulnerable to OCR attacks. Thus, we proposed to use inpainting algorithms to remove the contained text in the video frames, so that the OCR success rate can be reduced without introducing unwanted artifacts that displease the endusers. We implemented Ber...

Abuse of free Internet resources and services from false account creation, to spam, to identity theft, excessive bandwidth usage, or even vote stuffing online polls is a big problem. The Completely Automatic Public Turing Test to tell Computers and Humans Apart (CAPTCHA) controls access to resources but automated systems are increasingly adept at overcoming them. In this paper a method of acces...