User registration supports google reCaptcha feature. reCaptcha is a free service that protects your site from spam and abuse. It uses advanced risk analysis techniques to tell humans and bots apart.
To add google reCaptcha to your form, go to your form and enable reCaptcha support.
And add your reCaptcha Site Key and Secret Key in User Registration -> Settings -> Integraion.
If you donot have Site Key and Site Key already. To get the reCaptcha Site Key and Secret Key, go to https://www.google.com/recaptcha/intro/index.html and Click on get reCaptcha button on the top right. You will then need to register your site to get the site key and secret key.
After registering you get the site key and site secret.
After entering your site key and site secret in User Registration -> Settings -> Integration, you’ll get the reCaptcha support in the form. That’s all.