Ubuntu dos on port 22 how to fix?

Question

ubuntu

There is a server, I use ssh on port 22 to connect to it, it opens completely (I don’t know how to explain it, but when scanning through programs it says that it’s open, unlike 7777 where I have a game server)
So I decided to check what was running htop with DOS and I was shocked through LOIC on port 22, the server went under load 97 ...
How to make it so that the port does not close because ssh is needed and so that there are no problems with dos ..

Answer 1

Disable password login, disallow root login, use keys, fail2ban and other filters, at least change the port

Answer 2

Restrict access to port 22 only to your range of IP addresses??

Answer 3

change port to 23)

Answer 4

Five easy steps to secure ssh in Ubuntu. Part I
anosov.me/2011/07/five-simple-steps-for-ssh-protect...