When u tried to send a mail from yahoo.... most of the times u will be asked for Word Verification.This is to avoid the attack from bots.Below given is an example.
CAPTCHA stands for Completely Automatic Public [Turing] Test to Tell Computers and Humans Apart.A CAPTCHA is a program that can generate and grade tests that most humans can pass, but current computer programs can't pass. For example, humans can read distorted text as the one shown below, but current computer programs can't.
Several companies (Yahoo!, Microsoft, etc.) offer free email services. Most of these suffer from a specific type of attack: "bots" that sign up for thousands of email accounts every minute.A bot is a computer program that imitates a human being.This situation can be improved by requiring users to prove they are human before they can get a free email account. Yahoo!, for instance, uses a CAPTCHA test to prevent bots from registering for accounts.What do you say? Yes you are correct.As you think it is enough to verify an ordinary random text instead of this curved letters.But some image processing techniques can also be used by bots to know the word verification text.So inorder to make the bots unable to find out the text easily distorted text is used.Not just text even images of birds,bulbs,cars,coins... will be shown at random and an input is expected from the combo box.You can find out more at http://www.captcha.net/ Java has a plug-in named JCAPTCHA.You can integrate it into your applications.Hope u find this interesting....... bubyee
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