narayanprusty

This plugin adds Google’s No Captcha reCaptcha to WordPress comment, login, registration and lost password forms. A very short and sweet plugin which protects your website from bots trying to put spam comments, launch brute force attacks and creating fake accounts.

Google's No Captcha reCaptcha

This plugin adds Google's No Captcha reCaptcha to WordPress comment, login, registration and lost password forms.

Silkalns

WP Chill

Cristian Raiber

A very useful plugin for everyone using WordPress. Adds reCaptcha security to the WordPress login form, register form and comment form. This plugin could help your blog get rid of a lot of spam comments or brute-force attacks.
Nothing gets passed it if the reCaptcha doesn’t validate.
A few notes about the plugin:
<ul>
<li>Supports audio or image captcha types</li>
<li>Can generate the reCaptcha image / audio type in a number of predefined languages</li>
<li>Adds reCaptcha protection to the WordPress login form</li>
<li>Adds reCaptcha protection to the WordPress register form</li>
<li>Adds reCaptcha protection to the WordPress comment form</li>
<li>Adds reCaptcha protection to the WordPress recover password form</li>
</ul>

Uber reCaptcha

This plugin adds the reCaptcha form to the WordPress login form, recover password form, register form and comment form.

Google's No Captcha reCaptcha vs Uber reCaptcha