You mean how to keep people from within your house that you know are on your network from using the internet or people that are using you wireless router without your knowledge from using your internet? If the second one is what your talking aobut look at the directions for your router on how to enable WEP or WPA encryption, WPA is better for. I also disable SSID broadcast and use MAC addressing filtering to keep people off my network. Some routers are better than others as far as how many options they have. I have the Linksys WRT54G.
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