Linux Firewall (Netfilter)
Along, long time ago, the Internet was a friendly place and people only wanted to sit around their mainframe computers while holding each other’s hands, singing “Kum-ba-yah,” and browsing the few available websites. Everybody loved one another.
On a more serious note, the few original users of the Internet were focused on research and thus had better things to do than waste their time poking at other people’s infrastructure. To the extent security was in place, it was largely to keep practical jokers from doing silly things. Many administrators made no serious effort to secure their systems, often leaving default administrator passwords in place. That was then, and this is now!
Unfortunately, as the Internet ...