My desktop is connected to the router with a Cat-5 Ethernet cable (Cat-5 is short for Category 5 Inside Wiring, an old AT&T designation). It's the stuff used for standard network cabling. And my notebook in another room is connected wirelessly. Ever since then, when I boot up either computer, Windows warns me that there's no firewall installed. I simply cancel out and ignore this message. Am I O.K.?
A: Whoever told you to disable your Windows XP Firewall gave you dubious advice. The hardware firewall that's part of your router is an important part of securing your network, but it's not enough. Its role is primarily to prevent intrusions into your home network from the Internet. The problem is that outside threats aren't the only problem -- and sometimes not the biggest one.
A network protected only by a gateway firewall is in a condition security experts describe as "crunchy on the outside, soft and chewy on the inside." If one computer on the network is compromised, it in turn can easily infect any other PCs inside the network.
Compatibility should not be an issue. On my home network, the Comcast cable model is connected to a SonicWall router that includes a firewall. But every PC in the house is also protected with a software firewall with no problems. The Windows XP firewall is limited, though it's a lot better than nothing. The Norton and McAfee Internet security suites include more capable firewalls, though my favorite remains ZoneAlarm, from Zone Labs. Wildstrom is Technology & You columnist for BusinessWeek. You can contact him at email@example.com