Wireless Home Networking - Index of

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Part III: Installing a Wireless Network
Some routers use a technology called stateful packet inspection (SPI) firewalls,
which examine each packet (or individual chunk) of data coming
into the router to make sure that it was truly something requested by a
computer on the network. If your router has this function, we recommend
that you try using it because it’s a more thorough way of performing
firewall functions. Others simply use Network Address Translation (NAT,
which we introduce in Chapter 2) to perform firewall functions. This
strategy isn’t quite as effective as stateful packet inspection, but it works
quite well.
Airlink security
The area we focus on in this chapter is the aspect of network security that’s
unique to wireless networks: the airlink security. These security concerns
have to do with the radio frequencies beamed around your wireless home
network and the data carried by those radio waves.
Traditionally, computer networks use wires that go from point to point in your
home (or in an office). When you have a wired network, you have physical
control over these wires. You install them, and you know where they go. The
physical connections to a wired LAN are inside your house. You can lock
the doors and windows and keep someone else from gaining access to the
network. Of course, you have to keep people from accessing the network
over the Internet, as we mention in the preceding section, but locally it would
take an act of breaking and entering by a bad guy to get on your network. (It’s
sort of like it was on Alias, where they always seem to have to go deep into
the enemy’s facility to tap into anything.)
Wireless LANs turn this premise on its head because you have absolutely no
way of physically securing your network. Of course, you can do things like
go outside with a laptop computer and have someone move the access point
around to reduce the amount of signal leaving the house. But that’s really not
100 percent effective, and it can reduce your coverage within the house. Or
you could join the tinfoil hat brigade (“The NSA is reading my mind!”) and
surround your entire house with a Faraday cage. (Remember those from
physics class? We don’t either, but they have something to do with attenuating
electromagnetic fields.)
Some access points have controls that let you limit the amount of power used
to send radio waves over the air. This solution isn’t perfect (and it can dramatically
reduce your reception in distant parts of the house), but if you live
in a small apartment and are worried about beaming your Wi-Fi signals to the
apartment next door, you may try this. It doesn’t keep a determined cracker
with a supersize antenna from grabbing your signal, but it may keep honest
folks from accidentally picking up your signal and associating with your
access point.