How to add spam protection or recaptcha to forms?

Hi, I'm rather unclear on the following features:
- Spam Protection: How do I stop people from spamming our contact forms?
- Captcha: Is there a captcha feature available? 

We have a script on the form that protects it from basic spambots. Also, we do support Captcha fields:

How to Add a Captcha

Drawing Captcha

Moreover, the form can be set to accept unique submissions only.

How to Set Unique Submissions on a Form

https://www.jotform.com/security/