Warchalking

Warchalking is the drawing of symbols in public places to advertise an open Wi-Fi network.

Inspired by hobo symbols, the warchalking marks were conceived by a group of friends in June 2002 and publicised by Matt Jones who designed the set of icons and produced a downloadable document containing them.

[2] The word is formed by analogy to wardriving, the practice of driving around an area in a car to detect open Wi-Fi nodes.

That term in turn is based on wardialing, the practice of dialing many phone numbers hoping to find a modem.

Having found a Wi-Fi node, the warchalker draws a special symbol on a nearby object, such as a wall, the pavement, or a lamp post.