Hack 17. Map Nearby Wi-Fi Hotspots

Create interesting and useful maps of local and international Wi-Fi hotspot coverage.

Ever wonder how you can track the wireless networks in your neighborhood, or near your officeor how you can find free wireless connectivity when you're away from your home and office? I wondered the same thing, and so with the help of Eric Blevins, we created http://www.WiFiMaps.com for exactly this purpose.

WiFiMaps.com is a web-based, interactive map of wireless networks, with detailed street-level maps. If you're looking for open Wi-Fi nodes nearby, you can use the web site to browse geographical areas, perform various types of searches, and compare location or user statistics. The wireless node data is kept up to date by users who upload their wardriving data. Figure 2-11 shows a map of some of the Wi-Fi hotspots found in California, made with data contributed to WiFiMaps.com.

Figure 2-11. Wi-Fi hotspots in California

 

2.5.1. The Art of Wardriving

Wardriving is the geek sport of driving about (or walking, or biking, or even flying) while searching for wireless networks. The idea is to connect a GPS and wireless card to your portable computer, hop in the car, fire up your favorite wardriving program, and go out for a drive. As you move, the GPS records your location and some of the parameters of what your wireless card hears. The software on your portable computer takes note of the GPS coordinates and signal strength, and it usually beeps when a new network is found.

The term wardriving hearkens back to the script kiddie practice of wardialing, where a computer automatically dials phone numbers sequentially, looking for computer networks to crack into. Don't be misled by the aggressive sound of the term, however. The practice of wardriving can be carried out on an entirely passiveand legitimatebasis.

Mapping wireless networks can reveal patterns that are not always obvious. In the Wi-Fi map of California (Figure 2-11), we see the expected concentration of networks mirroring the populated parts of the state, but we also see the string of networks down the main highways.

Wardriving works because wireless networks broadcast beacon packets to identify themselves. Listening for these beacons does not require connecting to a network, and is (probably) legal. A number of people and businesses intentionally leave their networks open for use, and it is legal to connect to these networks. For instance, down the street from me is a network called "Beehive," which corresponds to the coffee shop of the same name that has a giant sign reading "Free Wireless Internet." A network named "Go Away" is most likely private. In between these extremes lies a vast gray area, where determining which networks are intended to be open is a policy question beyond the scope of this hack.

2.5.2. Collecting Data with NetStumbler

The most popular wardriving package for Windows is called NetStumbler, and it's available from http://www.netstumbler.com/. This package supports several different wireless cards, GPS logging, and a few extra features, and it's what I use when wardriving. On Linux and BSD, you can use Kismet, available from http://www.kismetwireless.net/, which has features similar to NetStumbler'sbut you will also need to run gpsd [Hack #57] . On the Mac, try MacStumbler (http://www.macstumbler.com/) or KisMAC (http://binaervarianz.de/projekte/programmieren/kismac/).

Unfortunately, getting wardriving software to work with different kinds of wireless hardware can be quite a challenge sometimes, and the details are beyond the scope of this book. For more information on getting your wireless network detection software working, take a look at Wireless Hacks (O'Reilly).

WiFiMaps.com parses most of the native wardriving log formats. NetStumbler will export to WiScan format, a text-based format, or its own binary .ns1 format. Regardless of which format you save your scans in, you'll want to upload them to WiFiMaps.com.

2.5.3. Uploading Your NetStumbler Logs

After your wardrive, take your resulting files and upload them to http://WiFiMaps.com/ by selecting the "upload" link at the top of the main page. You can create an account or upload anonymously. The upload parsing script will run once every night and publish the results in the morning. From there, you can determine the number of networks and individual points you have found, and you can browse the maps to see your results.

You can see from the image shown in Figure 2-12 that warchalking symbols are used to indicate the existence of security; the )( symbol shows an open network, while the ( ) stands for a closed network. The colors are also used to indicate security: red for closed, blue for open. Experiment with zooming in and out, and panning through your area.

Figure 2-12. Wi-Fi hotspots in San Francisco

The best part about WiFiMaps.com is that it's completely built on open source tools. The map-rendering uses MapServer [Hack #91], and the data is stored in a PostGIS database [Hack #87] . Both of these tools are covered in detail later in the book.

 

2.5.4. Warning, Traffic Ahead!

If you don't have lots of spare time, simply wardriving your commute can show you the networks on your route. You can vary your route sometimes, in order to cover a wider distance. Even covering the same area repeatedly is useful for picking up signals that are missed the first time or are very faint.

Wardriving can become a bit of an obsession. To maximize your coverage, print out the Wi-Fi maps of your areas and take them with you. Mark the roads you travel on, and drive through populated intersections a couple of timesthis will improve the quality of your collected data. A good source for other wardriving tips and tricks can be found at http://wardrive.net/.

Please pay attention to the road, to pedestrians, and to other types of hazards! Wardriving can be loads of fun, but make sure you enjoy it in a safe and productive way.

Drew from Zhrodague