rg305 - thank you for the suggestion. It's a bit beyond my capability at present: I shall have to work on it.
Rip - I am NOT convinced that a firewall will prevent all baddies from accessing the server. I AM convinced that it will help. as to Cisco, it is a bug-ridden system that has no relevance here. My firewall uses iptables. And use of a firewall does not "block everyone from finding it". It blocks (in my case) certain bad actors and several servers frequently used by them. To all genuine visitors, the sites are open.
Advising people NOT to use firewalls or to lower them for significant periods of time is, in my view and that of security experts, irresponsible.