NO LONGER MAINTAINED AND NOT RECOMMENDED, AS BOTS ARE ABLE TO RESOLVE CAPTCHAS BETTER THAN HUMANS. Based on Login Attempts check if captcha is necessary. It stores a permanent cookie and uses a table for tracking login requests.

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

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

This plugin adds helpers for the YinXiangMa CAPTCHA API

Simple, easy captcha for Sinatra

Implementation of captcha (Completely Automated Public Turing-Test to Tell Computers and Humans Apart) that is both easy to use and easy to customize/extend.

RedisCaptcha provides simple captcha that can be read by human.

RMagickCaptcha is a gem that implements captcha for using in Rails application.

Gem that uses RuCaptcha API to solver any type of captcha

Description of RailsCaptcha.

Captcha based on encyrpting and decrypting user data by mathematical operation

Death by Captcha Ruby implementation (HTTP API)

Quick little arithmetic plain-text captcha

My version of SimpleCaptcha

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

A very simple rack captcha middleware via captchator.com API

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.

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

Form protection with simple captcha calculations.

Helps humankind with simpler captchas