Although there are many applications available to keep your server secure and optimize its performance, but hiring a server management company will be a good option as they will implement few of their own system configurations too .. based on their experience
Well, to name a few that you should have running on your server, some as crons are:
I would also suggest doing the following:
Setup the firewall to only allow the IP addresses you put into the "allow.hosts" file.
Block port 22 for shell and setup some other random port in the 4 to 5 digit area.
Finally, disable a direct root login, instead, login as the admin user (you, using your main account) and then use 'su-' command to login as the 'superuser' into root.
Those are just some of the things you could do. They are common and necessary and will do for the most part unless you are running a very large and well-known site(s) that could be prone to more attacks than just a new site.
Hope this helps
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