Having your IP address isn't a big deal. Hackers don't target a specific address anyway, they target a range. I have ZoneAlarm running on my system at home, and it is shocking how many times I get probed every day. Very few of them are trying to communicate with my specific address, they are normally scaning block of addresses looking for systems listening on a specific port.
If you are running a Windows PC, I STRONGLY advise downloading and installing the free version of ZoneAlarm. It is easy to set up, easy to use, and very effective.
http://www.zonelabs.com/
For a simple web based test of some basic vulnerabilities of your PC, use Gibson Research Corporation's "Shield's Up!" test. It does a quick check to see if you are vulnerable to a few different attacks.
There is also some good information on how poor unsuspecting cable modem and dsl users PC's were used in Denial of Service attacks.
I don't agree with his assesment of how Windows XP will be the end of the world, but the rest is interesting.
Tom
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82 911SC Coupe