How to improve Linux security?

Question

linux

Consider clean versions of Debian 10 and (B)Ubuntu 16.

Which tools and configurations need to be tested? For example firewall configs?

Naturally, we will miss such obvious facts as less use of csgo roll, pron and other fake sites and applications, repositories.

Answer 1

Do not use the server as a machine for the user, developer, etc. And so put the minimum image, open ports 22 and 443, install a certificate for ssh and close cloudflare