Wireless Surveying on the Pocket PC
Pages: 1, 2


Warchalking is the practice of drawing symbols on walls to indicate a nearby wireless network. With the symbols, wireless users can identify the areas in which they can connect wirelessly to the Internet. Figure 6 shows the symbols used for warchalking. For more on this, check out

Is Wardriving Legal?

Before you do your own wardriving, be sure to check with the local authorities to see if it is legal. As far as I know, wardriving is not illegal in the U.S. However, in some countries, wardriving is an offense, and can be classified under the Computer Misuse Act.

One way to protect yourself when doing a wardrive is to disable DHCP on your computer or Pocket PC. Set a static IP address for your device so that when you are associated with an access point, the network does not assign an IP address to you. Technically speaking, so long as you have not been assigned an IP address by the wireless network (even though you have been associated with the access point), you have not joined the network, and so you cannot be held liable for trespassing into the network.

However, if you use DHCP for IP address and an IP address is assigned to you, your MAC address will be logged by the network. This makes you liable for your action.

Figure 6. Symbols used for warchalking

How Warchalking Came About

During the Great Depression in the 1930s, many people left their homes to look elsewhere for jobs. Some of these people came to be known as hobos. Because life was generally hard, there weren't many people willing to help these hobos; thus they were not welcomed. At that time, the hobos flocked to Texas because it was rumored that there was a town called El Paso known for its generosity to beggars. To avoid troubles with the neighborhood, the hobos devised symbols to communicate with each other so that they could know what to expect in the town. Figure 7 shows some original symbols devised by the hobos. Can you figure out what they mean?

Figure 7. Some symbols used by the hobos

Here are the answers:

  1. You will be beaten
  2. Man with gun
  3. Safe camp

You can visit the following web sites for more symbols used by hobos:

Related Reading

WarDriving: Drive, Detect, Defend
A Guide to Wireless Security
By Chris Hurley, Michael Puchol, Russ Rogers, Frank Thornton

Matt Jones, an Internet product designer, operates a web site that served primarily as the Londoner's online resume and portfolio. In June 2002, Jones combined the practice of using a sniffer tool to detect wireless network (wardriving or warwalking) with that of the hobos' symbols to come up with the symbols for wireless networks (as shown in Figure 6). Using these symbols, wireless users can then know if there is an available wireless network for their use. He was inspired by architecture students "chalking up the pavement" on his way to lunch. And during a lunch, Jones and a friend, who had recently been discussing hobo signs with another friend, came up with the notion of warchalking.

So the next time you see such a symbol on a wall or a sidewalk, you know that there is probably an available wireless access in the vicinity. Once you know about it, what can you do with it? To answer this question, you need to consider the legal and moral aspects of warchalking.

Warchalking, Legality, and Morality

Warchalking for wireless networks is an activity that is still legally debatable at the moment. First, drawing chalk marks on the wall may not constitute an offense (this depends on where you live; it is definitely considered an offense in Singapore if you do it without explicit permission). But the real concern comes when you discover a wireless network in a nearby home or business. Unlike wired networks, a wireless network has no clear boundary; hence, how does one define trespassing?

What happens if a wireless home network is not protected by any form of security or MAC address filtering? In this case, the wireless network is deemed to be "open" and may suggest that strangers are welcome to use the network. So should you connect to the network? There is no clear answer.

At the time of this writing, a bill (House Bill 495) was moving through the New Hampshire State Legislature that defined explicit boundaries. Under that bill, users would effectively be permitted to connect to open wireless networks. HB 495 recognizes that an open network is often a welcome mat. After all, if you were sitting in a public place such as a hotel lobby, airport, coffee shop, library, or conference venue and found an open access point, what would your first instinct be? Would you connect to the wireless network or find someone of whom to ask permission? Most users would assume that the network was put there for their use. HB 495 would still protect wireless network operators by requiring them to take some steps to secure their networks in order to be able to prosecute unauthorized users who connect to their networks. If this sort of legislation becomes more common, then the legality of warchalking and wardriving will be easier to evaluate on a case-by-case basis.

Wei-Meng Lee (Microsoft MVP) is a technologist and founder of Developer Learning Solutions, a technology company specializing in hands-on training on the latest Microsoft technologies.

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