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

Captcha based on encyrpting and decrypting user data by mathematical operation

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

Block repetetive requests from logged_in users and shows captcha.

Define questions and answers in a YAML file and validate your models with a single line of code. No more captchas or other stupid tricks.

Helps humankind with simpler captchas

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

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

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.

This library can help you create a captcha in your terminal application, which may be damaged by a large influx of requests.

Simple negative captcha for Rails

Antigate (Decode captcha service) wrapper for Ruby

Repackaged visualCaptcha's backend service, including translation and minor modification. Mainly for private use. Everything still belongs to original author: emotionLoop. ...

A smart captcha library

Ruby wrapper for Yandex.Cleanweb

Description of TinyCaptcha.

Simple negative captcha for Rails

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

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

you will get arithmatic sum with answer you just have to compare with ur user in controller