Directory of CAPTCHA Resources

Home > Computers > Internet > Abuse > CAPTCHA

A CAPTCHA is a type of test used to protects website services against use by automated programs that might abuse or otherwise take advantage of the service. The idea is to have a simple question that is easy for a human to answer, but difficult for a computer program. The standard technique is to ask users to type in text shown in an image. Typical applications include protecting registration and comment forms.

Resources in This Category

• CAPTCHA: Telling Humans and Computers Apart Automatically

  http://www.captcha.net/
  Includes demonstrations, research papers, and news.

• Dice Captcha

  http://dice-captcha.com/
  Users need to roll dice and answer the question to verify they are human with this free image based service. Provides a demo, FAQs and customization options.

• Inaccessibility of CAPTCHA

  http://www.w3.org/TR/turingtest/
  A W3C Working Group Note explaining how CAPTCHAs can present a major obstacle to users who have limited vision or a learning disability such as dyslexia. This document examines a number of potential solutions and alternative systems.

• JCaptcha

  http://jcaptcha.sourceforge.net/
  An open source Java framework for captcha definition and site integration. Project information, documentation, issue tracker, and download.

• reCAPTCHA

  http://www.google.com/recaptcha
  A captcha system that uses successful decodings to helps digitise books for online use. Background, and details on how to incorporate into a site. Source code in several languages, and plugins for popular blogging and CMS software.

• Securimage

  http://www.phpcaptcha.org/
  Open source PHP script for generating image CAPTCHAs with audio alternatives. Includes documentation, a gallery and an online demonstration. [LGPL]

• Sweet Captcha

  http://www.sweetcaptcha.com/
  Free customizable image-based service. Provides a FAQ.

• Wikipedia: CAPTCHA

  http://en.wikipedia.org/wiki/CAPTCHA
  Explains how captcha features can keep spammers from signing up for certain accounts online, such as email or weblogs. Explains how the system can be circumvented as well.

Related Categories

• Home > Computers > Internet > Abuse
• Home > Computers > Internet > Abuse > Comment Spam
• Home > Computers > Internet > E-mail > Spam > Preventing

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