Can you lock your wireless network on a mac?

Yep. Go into the router and click on the "Wireless" menu and disable "Wireless SSID Broadcast". It will be harder for others to see you then. But you will have to log into your wireless network every time instead of automatically as your computer won't be be able to see it now. If all your wireless items are one band (b, g or n) then just use that mode and then any one with the older "bands" can't get on. Go to WPA Personal. You can go to Linksys.com, Belkin.com, etc and read up on the "how to" that best fits you. You might try your routers company website and look it up there. Linksys has real good info.