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

This is how it looks on comment forms.
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.