How to secure your hosting from hacks?

Question

Network administration

I have a server in the Russian Federation, I provide hosting to companies, I have recently been puzzled by security, although the LLC does not want to spoil the reputation.
Everything is built on ISP, VMmanager+Billin+ISPmanager
What rules do you need to know first?

Answer 1

There is only one rule - do not allow a novice administrator to configure the server. No one will help you with advice, there will be a very big chance that because of your ignorance, something was overlooked or incorrectly configured somewhere. So hire a competent administrator (for example, from the same office that has your servers) and let him check what and how it is configured and where it can and should be redone.

Answer 2

No way. A competent administrator will save you. And that's not a fact.