Warchalking is the drawing of symbols in public places to advertise an open Wi-Fi wireless network.
Inspired by hobo symbols, the warchalking symbols were conceived by a group of friends in June 2002 and publicised by Matt Jones. The word is ultimately a reference to the 1983 film War Games. The film showed crackerss using software to dial randomly selected telephone numbers in the hope of finding a modem. This technique became known as wargames dialing (sometimes erroneously identified as wardialing; see also demon dialing), from which warchalking was later derived.
Having found a Wi-Fi node, the warchalker draws a special symbol on a nearby piece of public furniture, such as a wall, the pavement, or a lamp post. Anyone initiated in the ways of warchalking will recognise what it means and get online. In certain cities, the word bellum indicates the presence of an open node. If the node is later protected by some means such as encryption or if the node is no longer existent, the word bellum should be crossed out and replaced with the word pax. These words are Latin for war and peace respectively.