Researching Debian now as my business partner wants to potentially move to a more stable platform for the apps to run on. The problem is, is that the apps are the problem. Especially on unsupported free versions. B ut, willing to take on the challenge. Problems is I know basic unix and linux, but not Debian in specific (knew HPUX, Solaris, AIX, Gentoo, RedHat, Fedora, BSD/Digital Unix, SuSE Linux).
So, how to deal with attackers from the onset -- on ubuntu, portsentry is your friend, as is fail2ban. Iptables is a must know and use with ufw. But on Debian ...