I recently notices a rise in failed SSH login attempts on my server so decided to lock it down even more. Changing your SSH port is a easy way to add security to your linux box. This will be stop script kiddies from brute forcing your box (make sure you have a strong complex password). This will not stop all attacks, but it will help. I will be using Centos 7, but the process should be pretty much the same on most linux boxes.