Ruby wrapper for Yandex.Cleanweb

generate captcha by dalli,use the memcache

A library to make creating negative captchas less painful

A plugin to make the process of creating a negative captcha in Rails much less painful

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Simple captcha based on plain text questions.

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

Captcha form Jike API

Simple gem to add captcha or negative captcha to your Rails 3 application

Antigate (Decode captcha service) wrapper for Ruby

A captcha that uses images instead of garbled text

Wrapper for Captchabot.com

Captcha-Plugin for Rails

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

Implements view helpers for the ASIRRA CAPTCHA system for Rails-based websites

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

Anti-spam protection for your website

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.

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

Generates and verifies ascii art captcha.