Should I close my wireless network?
It use to be useful, but closing your Airport or wireless network (sometimes referred to as not broadcasting your SSID) is really no longer a real option when it comes to wireless security.
Unfortunately "Closed" networks, MAC access control lists, and reduction in transmission power are all more "feel good" security rather than real security. All these various approaches are dated and mistakenly lead to overconfidence.
WPA is your only real option if you value wireless security.
My recommendation is not to worry about broadcasting your SSID but use WPA. This will be more secure than a closed WEP encrypted network. Closing your network makes it very difficult for neighbouring networks to see which channels are free thus causing potential interference problems.
Another thing to consider is that a closed network is still broadcasting and therefore is detectable (regardless of whether it is broadcasting a SSID). If someone was determined to hack into your network, then not broadcasting your SSID and MAC address access control is not going to stop them.
WPA is virtually uncrackable (only really vunerable to a dictionary attack if a real word is used as a password) and therefore will stop the casual user and the determined hacker.
If you are really worried, don't use wireless just use wires.
For most newbies to wireless networking, not broadcasting an SSID and or MAC address filtering will only complicate matters especially if they are already having problems. Therefore if you are having problems with your wireless network, my suggestion will always be use WPA and leave it at that, the wireless network will be secure.