llavillaccama

The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms. It protects your website from spam by means of math logic, easily understood by human beings. 
This captcha can be used for login, registration, comments forms.
This plugin is based on the recapcha of google, for receive more information can visit the website: https://www.google.com/recaptcha
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JC Recaptcha

The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms.

webdesignby

Add Google’s latest simple checkbox reCAPTCHA to WordPress default login page. This plugin will help secure your wordpress administration area against brute force hacking attacks using the latest, simple and elegant ‘No Captcha’ reCaptcha checkbox from Google.
This plugin was created because some of the others I tested broke my login page on activation. This plugin is very easy to install and set up. I use it on multiple websites so it is tested regularly. 
Simply install, activate and enter your credentials from Google. 
https://www.google.com/recaptcha/admin
PHP 5 >= PHP 5.3.0 or Required

Webdesignby Recaptcha

Add Google’s simple checkbox reCAPTCHA to WordPress wp-admin login page.

JC Recaptcha vs Webdesignby Recaptcha