NATS has the option to use Google reCAPTCHA. Currently only V2 is suported. In order to use Google reCAPTCHA, you will need to setup your site with google and obtain the site key and the secret key. You can do so by going to this by going to the https://www.google.com/recaptcha/admin url.
During the initial development we only used the reCAPTCHA V2 -> "I'm not a robot" Checkbox option. Please feel free to try other options and let us know if you run into any issues.
Once you have the site key and the secret key, please follow one of the CAPTCHA articles to setup Google reCAPTCHA for the desired section.