Wireless Surveying on the Pocket PCby Wei-Meng Lee, author of Windows XP Unwired
Today, wireless networks are everywhere -- at Starbucks, Burger King, airports, and so forth -- and all provide wireless Internet access (for a fee). Finding commercial wireless operators is easy; very often, you'll see signage hanging outside a coffee house or on the walls of a hotel lobby. If not, when you power up your Windows XP computer equipped with a wireless card, it will display a list of available wireless networks. Examining the SSIDs will often allow you to identify the network operators instantly.
However, there are times when you can get free wireless Internet access -- if you know how to find the networks. This article will touch on the topic of wardriving and introduce you to some tools for locating wireless networks when on the road using a Pocket PC. It is useful as a guide to help you look out for wireless networks in places such as hotels, coffee houses, libraries, or even your neighborhood!
Wardriving, Warwalking and Warflying
A new term has been coined to describe the act of doing site surveys: wardriving. Wardriving involves people using their notebook computers or Pocket PCs (equipped with wireless cards and GPS receivers) and driving around a city (or a neighborhood) looking for the presence of wireless networks -- just for the fun or it, or to assess the security risks of wireless networks.
With a GPS receiver, wardrivers can catalog the exact location of an access point. Besides wardriving, there is also a term for people who perform site surveys via walking: warwalking. So warflying then will seem obvious to you; people fly on an airplane to do site surveys (for a great warflying story, see Philip Windley's weblog).
To see the wardriving efforts around the world, go to google.com and type in "wardriving."
Site Surveys, or Wardriving
A simple way to find wireless networks is to perform a site survey with your wireless network card. Doing a site survey is simple using either Windows XP's built-in capabilities or an advanced tool such as NetStumbler or MiniStumbler for your Pocket PC.
Check out the utility software bundled with your wireless card. Very often it comes with applications that allow you to perform site surveys.
NetStumbler and MiniStumbler
NetStumbler is a popular free wireless network discovery tool (written by Marius Milner, a San Francisco Bay area software developer) that runs on Windows-based computers. You can use NetStumbler for site surveys and it is also a useful tool for detecting unauthorized (rogue) access points.
You can download NetStumbler from www.netstumbler.com. Running NetStumbler will display a host of wireless access points detected.
Figure 1. Using NetStumbler to detect wireless networks
As shown in Figure 1, NetStumbler groups the access points detected based on channels and SSIDs. In this case, several access points were found running on channel 6. The MAC addresses of the access points are also displayed, together with other information, such as vendor of the access point, whether WEP was used, a signal-to-noise ratio, etc.
You can also use NetStumbler to display a graph depicting the signal-to-noise ratio of a given access point (see Figure 2). This is useful for helping a network administrator select the best place to position an access point for maximum coverage. To aim for maximum coverage, once an access point is mounted, install NetStumbler on a notebook computer and survey the areas that you would like to access point to cover. NetStumbler displays the graph in two colors -- green and red. If the graph displays in mostly green, then it means that the signal is strong. In general, always aim for lots of green color in your graph.
Figure 2. NetStumbler can display the signal-to-noise ratio for an access point
For Pocket PC, you can use the Pocket PC version of NetStumbler, written by the same author: MiniStumbler. Using MiniStumbler (see Figure 3) is much more convenient than using a notebook computer, as you can hide the Pocket PC in your, well, pocket. So the next time you see someone holding a Pocket PC pretending to do some serious work, he may just be spying on your wireless network!
Figure 3. Using MiniStumbler on the Pocket PC
If you do a site survey using NetStumbler (or MiniStumbler) and find a bunch of access points, you may be surprised to see the number of wireless networks that do not use any kind of security.
NetStumbler and MiniStumbler also include GPS support, so you can connect a GPS receiver to your notebook or Pocket PC and collect the location information for all of the access points you find. Feeding the latitude and longitude information to mapping software (such as Microsoft MapPoint) lets you plot a map showing the locations of the access points. See my book Windows XP Unwired for more details on how to use NetStumbler with GPS.
Check out the NetStumbler and MiniStumbler web sites to see if your wireless card is supported. NetStumbler generally works with wireless cards using the Hermes chipset. However, some cards that are not supported by NetStumbler (such as those from Cisco and D-Link) work under Windows XP. My Cisco Aironet 350 works well with NetStumbler. Unfortunately, my HP h4150 with integrated Wi-Fi does not work with MiniStumbler.
Another popular wireless survey tool for the Pocket PC is PocketWiNc. PocketWiNc works on Pocket PC 2002 and Windows Mobile 2003 platforms and supports the three wireless standards: 802.11a, 802.11b, and 802.11g.
Using PocketWiNc, you can detect wireless networks and measure the signal strength of each network (see Figure 4). It works on my HP H4150.
Figure 4. PocketWiNc in action
WiFiFoFum is another wireless survey tool for the Pocket PC. It is designed to run on the Windows Mobile 2003 platform. It was written using the .NET Compact Framework, so you need Windows Mobile 2003. I suspect you should be able to get it to work on Pocket PC 2002 devices as long as you install the .NET Compact Framework Runtime, but I have not verified this. One interesting feature about WiFiFoFum is that it is able to display the approximate location of wireless access points on a "radar" screen (see Figure 5). It is fun to see a wireless point drifting away from you as you walk farther away from an access point. This is a useful aid for optimally positioning your wireless access point.
Figure 5. Using WiFiFoFum
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