CAPTCHA is an abbreviation of C ompletely A utomated P ublic T uring test to tell C omputers and H umans A part, and CAPTCHA is copyrighted by Carnegie Mellon University. Following my previous article CAPTCHA & Intelligent Security - how to use CAPTCHA, reCAPTCHA & Audio CAPTCHA here are are few of the new versions of reCaptcha that are already in use.

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If you have used Yahoo! Chat for example, you must have seen this one:

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The user is asked to type in the characters (afef in this case) in an input area. The characters contained in the image is then matched to what the user has entered. In this case, if the user entered afef, then the system allows the user to proceed to the next section. If the user types in anything other than afef, the system will stop & show another image. This will continue until the user enters the characters that the image shows. The characters are not case sensitive, which means, small, capital or a combination of small & capital letters are allowed.

A more modified form of reCAPTCHA is also used very frequently these days. Mostly websites that have a large number of users logging in, or having a registration process could use these complex reCAPTCHA to prevent automated logins.

In this example, the image shows the symbols D O K V 9 M 8 . But the trick lies somewhere else! There are small pictures of cats in some of these alphabets or numbers. The user now has to look carefully and type only those numbers, alphabets or symbols that have the picture of cats. Thats O V 9 M in this case. Since all the individual characters D O K V 9 M 8 have some form of a picture attached to it, only a human eye could identify the ones with a cat in them. This makes the validation process even more stringent.

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If you want to study more about the Carnegie Mellon Universities CAPTCHA & reCAPTCHA project, visit the CAPTCHA official website here .

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