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Hack 23 Detecting Networks Using Handheld PCs

Easily monitor wireless networks while walking
around.

If you have a handheld PC,
you know how convenient it is. What you may not realize is that it
makes an excellent wireless testing device. If your handheld has a
Compact Flash or PC card slot, you can use a wireless card in these
slots.

If you have a
Sharp Zaurus or Compaq iPAQ running Linux,
then you're in luck.
Kismet
[Hack #31] runs well on
these machines, giving you the most powerful and tiny network
monitoring tool there is. When compiling Kismet for a handheld
platform, be sure to include the handheld optimizations. See the
Kismet documentation for details.

For Pocket PC 3.0 and 2002 users,
the author of NetStumbler has written a miniature version just for
Pocket PCs: MiniStumbler.

MiniStumbler can be downloaded from http://www.stumbler.net/. As of this writing,
the current version is 0.3.23. MiniStumbler supports
Hermes
chipset cards only (the Lucent/Orinoco/Agere/Avaya/Proxim strain).
There is currently no support for Prism or Cisco cards.

To install MiniStumbler, just copy the proper file for your Pocket PC
processor architecture from your host PC over to the Pocket PC. There
is no setup routine. Supported processor architectures include ARM,
MIPS, and SH3. Check your system documentation if you
don't know which one your handheld uses.

As with NetStumbler [Hack #21],
you'll want to set some options the first time you
launch it. There are two menus at the bottom that
you'll want to check out. The first is Opt, as shown
in Figure 3-16. Make sure that Reconfigure
card automatically and Get AP Names
are both checked.

Notably missing from MiniStumbler is MIDI support for audio feedback.
However, you can still set the scanning speed, by clicking on the
Spd menu, as shown in Figure 3-17. Generally, you want to set it to the fastest
possible speed.

With MiniStumbler's options properly configured,
you're ready to discover wireless networks. As long
as your wireless card is installed, MiniStumbler will immediately
start scanning for networks. A typical scanning session looks
something like Figure 3-18.

If you've ever used NetStumbler, you should be right
at home. The data is displayed in exactly the same way, using the
same color scheme for the networks it has detected (green, yellow, or
red to indicate signal strength, grey for networks out of
range, and a tiny lock icon for networks using
WEP). If you need to pause
the scanning process, simply click on the green triangle in the
bottom menu.

While the tiny screen on a Pocket PC is wonderfully portable, it
makes viewing large amounts of data sometimes painful. In order to
see all of the data in MiniStumbler, you have to scroll to the right.
This includes signal strength, SNR, and noise levels.

MiniStumbler does not support any of the
visualization views in NetStumbler, so you can't get
a graph of wireless signal over time. However, there is support for
location logging using a
GPS. Click on the
GPS menu (Figure 3-19) and
select the COM port attached to your GPS. MiniStumbler will then show
latitude and longitude locations for all of your wireless networks as
it finds them.

Obviously, a GPS can only effectively be used for outdoor network
detection. But the extreme portability of Pocket PCs make them ideal
for performing informal site surveys, checking for unauthorized
access points, or establishing the coverage area of your wireless
network. MiniStumbler may be missing many of the handy features of
NetStumbler and Kismet, but it is simple to use and far better than
the system client for finding networks.

Roger Weeks