To follow on from Metaphysical : hackers, or at least the kind you should be worrying about, tend not to 'target' your machine per se. Indeed, their only real objective where your machine is concerned is to take control of it so it can be used to launch DDoS attacks against much larger victims. They will passively port-scan whole subnets (blocks of addresses), and anything interesting will pop up in their logs. For instance, say your machine was a Windows box, that for some reason was configured so that port 139 was accessible through its public IP address: the hacker would have a note of this, and would almost certainly return to do some more poking. The other obvious example is that of spammers scanning networks for open mail relays, however as a domestic user you're unlikely to be running one. Contrary to popular belief, Zone Alarm is not a particularly good firewall product, but then no software products really are. It comes down to balancing economics against what you need to protect: The only real solution if you're paranoid is a cheap hardware firewall/router, and you'd be connected through this, though it'll cost you about �100. As Metaphysical states though, network security is never totally secure - it will just make you seem less attractive compared to the thousands of insecure computers.