7.1 Hacks #86-100
When
it comes to wireless networking, there is no such thing as physical
security. You might be able to lock down the physical network
infrastructure of a business or other facility, but radio waves pass
through walls, carrying your network data with them.
Don't delude yourself by thinking that a low-powered
access point won't reach much further than your
parking lot. Remember that although you may not see your network
using a laptop outside your building, someone with a large enough
antenna can likely read your network traffic from a mile or more
away. I have personally seen a simple 24 dBi dish detect hundreds of
wireless networks from the top of Queen Anne hill in Seattle. These
were networks with SSIDs like
"Linksys" and
"default," which obviously were
coming from low-end, consumer-grade access points without any
external antennas. I certainly couldn't have made a
reliable network link to them, but I could have passively logged
their traffic from miles away quite easily. Short of wrapping your
entire building with a metal screen to build an effective Faraday
cage, you should expect the signal of your APs to leak out well
beyond your immediate vicinity.
This chapter is devoted to workable methods for controlling access to
your wireless network. A control mechanism could be something as
simple as a WEP key, or as complex as a captive web portal with a
RADIUS backend. We will also look at several ways you can protect
your own data when using other wireless networks, even if those
networks are completely public and open.
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