reCAPTCHA is a free service that protects your website from spam and abuse. reCAPTCHA uses an advanced risk analysis engine and adaptive CAPTCHAs to keep automated software from engaging in abusive activities on your site. It does this while letting your valid users pass through with ease.
Your site comes with the Google reCAPTCHA module pre-installed.
Google reCAPTCHA challenges are automatically added to web forms, so long as the reCAPTCHA module is properly configured. You do not need to take any steps to add a reCAPTCHA challenge to web forms.
Note: You will not see the reCAPTCHA challenge when logged in as an authenticated user. To test the web form with reCAPTCHA enabled, log out or enable your browser's privacy mode.