reCAPTCHA
reCAPTCHA v2

reCAPTCHA v2 is a new version of reCAPTCHA. Instead of entering text users can now use a single click to confirm they are not a robot.

reCAPTCHA is a free CAPTCHA service (http://www.google.com/recaptcha) that helps protect your site against spam, malicious registrations and other forms of attacks where computers try to disguise themselves as a human. reCAPTCHA is currently one of the best ways to protect online forms from spammers.
Download (Last update: April 10, 2015)
reCAPTCHA Extension

Requirements:
Works best with WYSIWYG Web Builder 10.3.4 or higher