I'm running a server using OpenVZ for a few websites. Nothing in HN except for sshd. A VM for Varnish, a VM for MySQL and a few VMs each for one website (running Apache/PHP). Now I'd like to secure this server, mostly from network attack (I think).
What I should do? I see that I should not install Selinux in HN. Installation of CSF seems complicated (needs a few iptables rule fine-tunes).