CAPTCHA stands for the Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHAs are tools you can use to differentiate between real users and automated users, such as bots.

CAPTCHAs provide challenges that are difficult for computers to perform but relatively easy for humans like clicking on a checkbox or a puzzle to solve.

For the purpose of authentication, there is a default CAPTCHA as well as Google reCAPTCHA provided.

You can enable it from the Admin settings>>System>>Module>>Client module and enable the captcha on register.

Refer to the following link to configure Google reCAPTCHA: https://www.google.com/recaptcha/admin/create

This will allow you to generate the required site and secret key 

These details have to be added to your Vision Helpdesk portal as shown below:

On configuring this, you will be able to use the Google reCAPTCHA on your client-facing portal to avoid spamming.