How to make the server not give a response when accessing the domain directly?

Question

Domain Name System

Hello.
A bunch of such a domain registered dns cloudflare, cloudflare refers to the server. But the question is next. In the case when they find out the real IP of the server where the site is located, they access it directly (bypassing cloudflare), then the server gives the site. I know what can be done so that it does not give. In the manuals from Google I read the following: "You assign CF to the domain. Set up your hosting. Set up CF for your hosting." But I don't understand what kind of CF. PS on the server is Plesk Panel.
Pliz help. I would be grateful for any answer. Thank you.

Answer 1

CF = cloudflare
On the server, deny access to your site for everyone except ip cloudflare. They have a list in the documentation.