For those of you who have not tried it, I was really impressed with ZoneAlarm. I have a dial-up 56k and generally stay connected for 4 to 8 hours at a time before something becomes "unconnected". ZoneAlarm alerted me to numerous incoming requests on ports which I did not even know existed. Probably something on the order of 20 or so incoming requests in the most recent 10 hours of internet connection. I like it so much, I think I am going to buy the Pro version.
I think if you do a Google search you can find it, or go to ZDNet and you can get it there.