A: If you let your neighbors onto your unsecured Wi-Fi network, you run a couple of risks. The most important: If you haven't properly secured the computers on your home network, a neighbor could gain access to your files. In the worst-case scenario -- unsecured Wi-Fi and Windows file-sharing turned on to allow access to anyone on the network -- everything you have is wide open to anyone within range with a Wi-Fi-equipped computer.
A more remote risk is that a neighbor could use your network to send spam or to hack into other people's networks, and the misdeeds might be traced back to you.
STEALING IS STEALING. Fortunately, you can easily prevent these problems. In addition to enabling Wi-Fi security, you should run firewall software on every machine, even if your network router includes a firewall. And if you enable file sharing, use extreme care in regard to what folders are shared and who has access to them.
Taking advantage of your neighbor's unsecured network without permission is definitely unethical and possibly illegal. In effect, you are stealing service paid for by your neighbor. Admittedly, the risks remain low, because few people pay attention to home network access logs, where the intrusion would readily show up. But just because you can get away with it doesn't mean you should. Using the access to get into a neighbor's computer would almost certainly violate one or more of several state and federal laws. Wildstrom is Technology & You columnist for BusinessWeek. You can contact him at firstname.lastname@example.org