From: "Peer Stefan"
If it is a real human cracker (!= script kiddy), who tries to crack just this single system, he/she will find a way into it.
Now that is rather defeatist, a real cracker has to way up the cost/benefit, if you have battened up all the exploits with scripts, have minimised the services they can connect to, and are tracing back their failed attempts, you can make it more trouble than it's worth. Their attempts will alert you to their previous victims, and they are likely to loose more boxes than they gain by attacking your machine. Unless they have a particular reason, or an axe to grind against you, logic dictates they move on to a softer target, as if they do break in, you will just pull the box and reinstall. I think if you had said, network, I'd be more inclined to agree, it is very difficult to close all the holes on a variety of systems offering large number of services. Once they're in they can probably add back doors faster than you can close them, and usually management are relectant to shut down the entire network for any length of time in response to such an incident. Of course if it becomes 'personal' then DoS attacks become a problem, but also you could try a Linux Virtual Server set up and learn their tricks and watch them operate in a sacraficial environment. Rob