CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a frequently used method that can prevent spammers and bots from posting comment and e-mail spam. Most end users are not aware of the term, although they may use some sort of CAPTCHA while submitting comments or sending e-mail messages through various forms. This article deals with the most popular WordPress CAPTCHA plugins that protect sites from spammers on WordPress based blogs
reCAPTCHA is an anti-spam technology from Google.One of the best anti spam plugin for wordpress. It uses a captcha to prevent comment, registration, and email spam.
SI CAPTCHA Anti-Spam wordpress plugin adds anti-spam methods to WordPress on the forms for comments, registration, lost password, login.
SweetCaptcha is a free Captcha plugin for wordpress. It protects Registration form,Comment form,Login form,Lost password form and Contact Form 7.
Secure CAPTCHA allows to distinguish between form submition made by human and script (robot, bot, program etc.). It gives you ability to reject all form submitions made in automatic way.
KeyCPTCHA is a free wordpress plugin providing effective protection by means of highly attractive and interactive CAPTCHA. it can entertain your visitors with a nice and pleasant CAPTCHA game.
Text Captcha uses riddles and math to prevent spam.This plugin comes with 10 predefined questions and the ability to add more.
Captcha wordpress plugin allows you to protect your website from spam using math logic which can be used for login, registration, reseting password, comments form.