Another thing you can do for securing a wireless network is to turn off "Broadcast SSID" SSID is the "name" of your wireless network. With the Orinoco wireless card I have, I can set it to look for the SSID "any" and it finds all wireless networks that broadcast the SSID.
If you understand IP addresses, turn off DHCP, and manually set the IP addresses on your computers.
Get rid of default settings on your wireless network. Most people that go around trying to log onto other peoples wireless networks are going to know the default settings for a lot of different brands of wireless equipment.
These are the ways that I secured my wireless network, and I also filter based on IP addresses. I only allow three through my router, one for each computer.
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