This article goes into some detail about detecting those pesky
script-kiddies and protecting your system. Friendly to people just
getting started with securing their machines and networks:
"You're a hot shot. You know how to use Linux and hey,
you even got that modem working. People think you're smart because
you know how to use Linux. But then one night, you're sitting in
front of your computer (the one that has the always-on cable modem
or DSL connection) and being the smart person that you are, you
said that you didn't need security. Well, sure you did a little
tweaking on that /etc/inetd.conf file and hey, it looked good.
But for some reason, someone slipped past that defense and
connected to port 80. Oh, yes that's right, that's your apache web
server running there in full daemon mode, not even protected by
inetd. What you did is inexcusable. Why is that? Because before you
could click on Bill Gates on that famous linux game (what is it
called?) that hacker just downloaded or caused some type of network
traffic in excess of 15 megabytes.