He has a utility that scans for access points which gives details about what the SSID is, what type of wireless encryption is used, the channel being used and the signal strength. The utility comes with the wireless card but XP comes with a Windows version and Linux comes with a few wireless analyzing tools. SSID broadcasts and lack of encryption allows hackers (or neighbors) easy access to the wireless network. If the type of encryption used is WPA, then SSID broadcasts are not a significant security issue. It is best to secure the wireless network because of possible legal problems due to illegal activities by hackers or neighbors such as copyright infringement (illegal file transfers or music or movies or whatever).