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

Merb plugin that provides resource access rate limits and captcha'ing

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

It's a Rails Captcha Engine for Rails 3 applications.

This gem enable to use Captchme. Anti spam, Monetize captcha and Audience qualification

Simple reverse captcha solution that consist in create a hidden field that should be always empty.

Simple Audio Extension to Simple Captcha

Block repetetive requests from logged_in users and shows captcha.

My version of SimpleCaptcha

wxianfeng_simple_captcha is captcha for rails,modified from simple_captcha .

Ruby wrapper for Yandex.Cleanweb

SimpleCaptcha is available to be used with Rails 3 + 4 or above and also it provides the backward compatibility with previous versions of Rails.

This version include two important page 'Contact' and 'Register' with the 'Math-Captcha' method submit for prevent hacker attack.

Russian Post tracking toolset, consisting tracking form bot (since Russian Post is too retarded for normal API) and captcha solver/recognizer.

HumanDetector is a friendly logic captcha for Rails the doesn't require any external system dependency (e.g. external captcha API connections). It uses a simple question that any 7 or more years old human can understand, but that a spambot will not be able to answer. This Gem supports Ruby v1.9.2 and Rails 3.0.x.

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.

This is a gem wrapper for tiny captcha in C with no dependencies.

A captcha verification approach for Rails apps, directly integrated into ActiveRecord’s validation mechanism and providing helpers for ActionController and ActionView.

SimpleCaptcha is the simplest and a robust captcha. Its implementation requires adding up a single line in views and in controllers/models. SimpleCaptcha is available to be used with Rails2.0 or above and also it provides the backward compatibility with previous versions of Rails.

A captcha verification approach for Rails apps, directly integrated into ActiveRecord’s validation mechanism and providing helpers for ActionController and ActionView.