Warchalking 101

If you've been following Wi-Fi, you've no doubt heard about "warchalking," the act of marking buildings and sidewalks with chalk to let others know about the availability of Wi-Fi access. More urban myth than reality, the warchalking phenomenon represents a growing reality: Free and open Wi-Fi networks are out there. The art is in finding them.

Though warchalking is lost on non-geeks, many Wi-Fi users are discovering that in dense urban areas, especially those with retail businesses underneath multi-unit apartment buildings, it's pretty common to find an open wireless networks, thanks to the generous (or careless) neighbors upstairs who haven't locked down their wireless networks.

In 2002, London-based IT consultant Matt "Blackbelt" Jones came up with an idea for Wi-Fi users to help each other get online. Jones proposed marking sidewalks, walls, or telephone poles where networks could be found with a set of chalk-mark symbols based on the old sign language that hobos used to alert one another to food, shelter, or potential trouble during the Great Depression in the 1930s.

Jones dubbed this practice "warchalking," a pun on "wardialing," introduced in the 1983 movie Wargames, in which a young hacker has his computer automatically dial all the phone numbers in the area looking for other computers. Geeks termed the practice "wardialing." Add that familiar erasable writing technology and you wind up with "warchalking." Here are the universally accepted trio of symbols for warchalking:

The most common symbol, used to represent freely accessible open Wi-Fi nodes, are two reversed parentheses, placed back to back. Less common are two variations of symbols for closed networks, both use a circle -- empty for closed with an unknown access method, or with a W inside to indicate the node is protected with WEP or WPA. In the latter case, if known, the warchalker will list the SSID for the network and contact information for the person or business that can grant access.

Despite a rush of media attention in the early days of Wi-Fi, warchalking was and is more a mental exercise and Internet conversation topic rather than a real-world phenomenon. You'll find a few marks here and there in London, New York, and San Francisco, but most have been made by the network owners themselves -- to draw attention to their businesses that have free and open Wi-Fi access -- rather than passers-by.

Most of the world's open networks aren't marked, but there are tools and software that make finding them easy. Read on to find out how you can find free and open nets, and whether accessing them is legal.