What is CAPTCHA?
The term CAPTCHA, based upon the word Capture, is a type of challenge-response test used in computing to ensure that the response is not generated by a bot. The process usually involves one computer asking a user to complete a simple test.
Using a CAPTCHA Script on a website is a great way to ensure that response is made by a real person and not by a spambot and it helps prevent automated abuse of your site such as comment spam.
There are many CAPTCHA scripts available, lets dig into the list together.
Image Based CAPTCHA
slideLock adds a jQuery UI slider along with labels and notes. The user simply slides the form to unlock the submit button and then both client side and server side validation techniques ensure secure submission of the form.
Stop spam and help digitize books at the same time! The words shown come directly from old books that are being digitized.
identiPIC is a photo CAPTCHA system whereby a website visitor has to identify a picture to proceed. The system is typically used on web forms to block spambots.
A lightweight CAPTCHA jQuery plugin which works with a simple click.
Ajax Fancy Captcha is a jQuery plugin that helps you protect your web pages from spammers. If offers an intuitive way of completing “verify humanity” tasks. In order to do that you are asked to drag and drop specified item into a circle.
Clickcha is a unique CAPTCHA system that more secure than traditional text based CAPTCHAs yet easier to use. Clickcha is currently available as plugin for WordPress and bbPress. It can also be integrated into any CMS using the simple Clickcha API.
Don’t read, just drag the right option into the block hole.
Securimage is an open source free PHP CAPTCHA script for generating complex images and CAPTCHA codes to protect forms from spam and abuse. It can be easily added into existing forms on your website to provide protection from spam bots. It can run on most any webserver as long as you have PHP installed, and GD support within PHP.
It uses a distorted point for human verification. It is easy to notice a slightly distorted point over an image. Its obviously a good option to click once instead of typing 5-6 letters. Look at the demo for better understanding.
Internet Captcha is a flash based CAPTCHA script for ASP and PHP designed to protect your HTML forms. It comes with a friendly configuration screen to edit interface and security level.
- http://www.tipstricks.org – Classic ASP based CAPTCHA
- http://www.spamerator.com – Spamerator can be integrated with any language including PHP, VB, ASP/.NET, Java.
- http://www.captcha.cc – Free service to place very hard CAPTCHA images in front of a form submission.
- http://rodomontano.altervista.org/engcaptcha.php – Static and animated CAPTCHA script generator.
Text Based CAPTCHA Scripts
Its a web service and comes with a unique API. Whenever you require a logical question, it requests to the server and the server returns an XML response containing a randomly selected question and answer.
A method of using a question / answer CAPTCHA system for determining whether one is dealing with a human visitor or a naughty robot.