A CAPTCHA is a program that can tell whether its user is a human or a computer. CAPTCHAs are used by many websites to differentiate between the bots (automated program) and the human. The main motive behind using the CAPTCHA is to prevent abuse from "bots," or automated programs usually written to generate spam. The CAPTCHA basically uses images in distorted form that is difficult to read by th...

This study focuses on a machine learning approach to the CAPTCHA recognition problem that requires minimal preprocessing of inputs. Both the feed-forward neural nets and the self-organizing maps used in this study took the raw image pixels as input with only simple segmentation and translation performed in advance. The models were trained and tested on four and five letter CAPTCHAs using either...

We present a new method for image taxonomy. Our formulation shows how the combination of automated metadata-based analysis and knowledge-acquisition tools can help build better image search applications. We build on top of existing metadata-based techniques to image taxonomy and combine them to human assistance, in order to guarantee some minimal level of semantic soundness. Knowledge from huma...

-------------------------------------------------------------ABSTRACT-------------------------------------------------------A novel technique of Captcha is regenerated by using composite images that are generated in the given data base. Captcha is a type of challenge response test used in computing to determine whether or not the user is human. Captcha are used to prevent bots or automated prog...

CAPTCHA is an important technology to prevent auto-script attack. Currently most of the CAPTCHA systems are text based, which firstly distort, rotate different characters and then use some obfuscation, aiming to make the text difficult to be recognized by autoscript while still can be learnt easily by real users. However, such kind of CAPTCHA schema either too simple, which can be attacked easi...

CAPTCHAs is Turing test are used to distinguish whether a user is a human or a computer. Till today huge number of CAPTCHA schema have been suggest or put forth and applied on miscellaneous websites to secure online services (SOS) from automated decaptcha programs. So development of a good CAPTCHA scheme that is both secure by automated recognition and human usable is an important research prob...

CAPTCHAs is an interesting of research are short for Completely Automated Public Turing test to tell Computers and Humans Apart. The purpose of a CAPTCHA is to block form submissions from spam bots –automated scripts that harvest email addresses from publicly available web forms. We introduce a new CAPTCHA which is based on identifying the color of image, object or background. This actually req...

A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a widely used security defense mechanism that is utilized by service providers to determine whether the entity interacting with their system is a human and not a malicious agent. Motivated by recent research which underpins the necessity for designing more userfriendly CAPTCHA, this paper investigates the ...

With data theft and computer break-ins becoming increasingly common, there is a great need for secondary authentication to reduce automated attacks while posing a minimal hindrance to legitimate users. CAPTCHA is one of the possible ways to classify human users and automated scripts. Though textbased CAPTCHAs are used inmany applications, they pose a challenge due to language dependency. In thi...