WIRELESS NETWORKS
Finding 802.11 networks
Lisa Phifer
08.30.2004
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If your company hasn't yet taken the 802.11 plunge, that doesn't
mean that your office is Wi-Fi-free. Unless you're far from other
businesses, 802.11 APs owned by neighboring companies may transmit
signals that reach your location. Employees may have deployed 802.11 on
their own, using inexpensive APs or peer-to-peer connections between
laptops. Vendors, contractors, customers and other visitors may carry
802.11-enabled devices into your office without even realizing it. In
fact, odds are actually pretty darn good that 802.11 has found its way
into your office.
How can you tell? Try using a basic WLAN discovery tool, commonly
referred to as a "Stumbler." Such tools are both freely available and
easy to use. All you need is a laptop with an 802.11 network adapter
and a discovery tool that supports your OS and adapter. Here's a short
list of freely available "Stumblers" to help you get started:
These tools will identify 802.11 infrastructure APs or ad hoc peers
transmitting in your vicinity. It's possible to "stumble" on a desktop,
but you'll probably want to use a laptop to wander your office, since
results vary depending upon distance from the transmitter. When you
find an AP or peer, track it down by walking in the direction of
increasing signal strength. Don't forget to look upstairs and
downstairs in a multi-floor building. You'll also want to repeatedly
spot-check over time -- if that gets too labor-intensive in a large
facility, consider using a wireless IDS instead.
If you discover 802.11 WLANs that don't belong to you operating
nearby, there's little you can do except be aware they exist and warn
employees not to connect to them. If you find unauthorized APs or
adapters installed in your facility or on company laptops, you can take
steps to eliminate them or make sure they're being used securely.
Either way, forewarned is forearmed, so stop, look, listen and discover
what's out there.
About the author: Lisa Phifer is vice president of Core
Competence, Inc., a consulting firm specializing in network security
and management technology. Phifer has been involved in the design,
implementation, and evaluation of data communications, internetworking,
security, and network management products for nearly 20 years. She
teaches about wireless LANs and virtual private networking at industry
conferences and has written extensively about network infrastructure
and security technologies for numerous publications. She is also a site
expert to SearchMobileComputing.com and SearchNetworking.com.
Do you have comments about this article, or suggestions for Lisa to
write about in future columns? Let
us know!
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