Hello, @edGiantSquid

There is no specific IP address that you should whitelist. You can block every IP address that makes unsuccessful ssh authentication as this is clearly not a legit traffic.

You can also look into changing the ssh port and make only the pubkey authentication is enabled leaving the password authentication disabled in order to keep things safe. Also make sure everything on the droplet is updated and you’ve blocked/closed all the ports which are not used.

Brute force login attacks are one of the most common ways for a server to be compromised. This tutorial shows you how:

• How To Configure SSH Key-Based Authentication on a Linux Server

Hope that helps!

Regards,
Alex