Captcha To Protect From Automated Register Bots

[linuxmalaysia]

Captcha To Protect From Automated Register Bots

A CAPTCHA is a type of challenge-response test used in computing to
ensure that the response is not generated by a computer. The process
involves one computer (a server) asking a user to complete a simple
test which the computer is able to generate and grade. Because other
computers are unable to solve the CAPTCHA, any user entering a correct
solution is presumed to be human. A common type of CAPTCHA requires
that the user type the letters or digits of a distorted image that
appears on the screen.

More about Captha
http://en.wikipedia.org/wiki/Captcha

This websites can be used to genarate captcha.

reCAPTCHA

http://recaptcha.net/

reCAPTCHA is a free CAPTCHA service that helps to digitize books.

A CAPTCHA is a program that can tell whether its user is a human or a
computer. You've probably seen them — colorful images with distorted
text at the bottom of Web registration forms. CAPTCHAs are used by
many websites to prevent abuse from "bots," or automated programs
usually written to generate spam. No computer program can read
distorted text as well as humans can, so bots cannot navigate sites
protected by CAPTCHAs.

White Hat Web Design PHP Captcha Security Images

http://www.white-hat-web-design.co.uk/articles/php-captcha.php

This script generates images (known as "Captcha's") which contain
security codes used for protecting a form from spam bots. By encoding
a 'password' inside an image and asking the user to re-enter what they
see you can verify the user is a human and not automated software
submitting your form.

[linuxmalaysia]