CAPTCHA, especially Text-based CAPTCHA, is the most widely used for security over the
online environment in the present. That was used for identification automatic program …

CAPTCHA is the most important method for protecting malicious software gains access to
the system through the Internet. However, this technique has many difficulties for users to …

Presently, CAPTCHA is an important mechanism to gain access to the required system.
However, there are some difficulties for users in typing CAPTCHA although they are …

There is a substantial emphasis on security design of Text based CAPTCHA by way of
providing the security at pre-processing layer, segmentation layer and character recognition …

For more than a decade, CAPTCHAs are around to enhance the security level of a broad
range of web-based activities such as ecommerce, online polls, etc. Although, the literature …

CAPTCHA (Completely Automated Public Turing Test to tell Computers and Humans Apart)
is a kind of test which is commonly used by different websites on the Internet to differentiate …

CAPTCHA technology is at a boom in the field of information security. When text CAPTCHAs
are at a point of break down, it is the time for the image based CAPTCHAs to get a pace. But …

In this Paper, we have proposed a new captcha based on digits and symbols. It is based on
the facts that it is difficult for the machine to interpret symbols and perform the tasks …

CAPTCHA is a security technique used widely over the Internet to verify whether the end
user is a human. Text-based CAPTCHAs are the most commonly used. The security of text …

In this paper, we present a survey of different CAPTCHA types. Then we address the
problem of the CAPTCHA userability. In the experiment, the Internet user response to solve …