A simple and fast image captcha generator that uses opencv and memcached.

Simple captcha

A captcha that uses images instead of garbled text

A honeypot style captcha extension for ActiveRecord. Simple one-line inclusion in the model combined with a simple form field should trap the bad guys in the molasses.

ALTCHA is a free, open-source CAPTCHA alternative that protects your website from spam and abuse

Simple Audio Extension to Simple Captcha

This is a Captcha gem for Rails Applications. It drawing captcha image with C code so it no dependencies.

To help with keep the bots at bay this gem helps you easily add honeypots to forms and/or obfuscate your form field names

SimpleCaptcha is available to be used with Rails 3 or above and also it provides the backward compatibility with previous versions of Rails.

API to interact with BrandCAPTCHA http://www.pontamedia.com/en/brandcaptcha/

A simple and custom captcha for Rails3.

Submit captcha images and retrieve the text as a string.

ZeroCaptcha allows companies to solve captchas with artificial intelligence software, which is faster than humans and very accurate

This is a Captcha gem for ruby. It drawing captcha image with C code so it no dependencies.

Block repetetive requests from logged_in users and shows captcha.

Unity Captcha is a gem that use two levels of Captcha. First level is about Left Hemisphere: Logic and Math. Second level is about Right Hemisphere: Intuition and Drawing. This two levels functioning in complete harmony creates unity and this is the base design of this Captcha.

A Rails captcha gem that attempts to determine whether or not a user is human.

Captcha Client for YunPian.com

Wrapper for Captchabot.com

Ruby wrapper for Yandex.Cleanweb