Wireless networks are everywhere these days. Coffee shops offer access, libraries offer access, shopping malls offer access, not to mention that most homes and businesses have a WiFi network or two deployed.
The problem with WiFi is that it does not respect boundaries the way us humans do, and the wireless signal tends to spill over into surrounding areas. If the security on the wireless network is not strong enough, this spillage will allow people nearby to use the wireless connection.
In the early days of WiFi, and before people really paid too much attention to security, there was a practice called "Wardriving" where folks would drive around neighbourhoods with WiFi scanners looking for insecure networks. The term is an adaption of the old "Wardialing" from the 1980's, where one would dial random phone numbers looking for a modem to hack into.
A subsequent evolution of the Wardriving concept is now called Warchalking, and is the practice of marking the status of a WiFi network on the surrounding buildings, pavements or lamp posts. The markings, originally done in chalk – hence the name – alert others to the network name, bandwidth and security level of the WiFi signal spilling over.
So, if you happen to see a warchalk symbol outside your house or office, you should probably check your WiFi network security otherwise you might be unwittingly sponsoring Internet access to passers by.
