war-chalking

The practice of using chalk marks similar to hobo signs to indicate the
nearby presence of a wireless Internet access point, a boon to strolling
hackers with laptops. The concept was first floated in early 2002 and was
instantly seized upon with cries of glee by hackers all over the portions of
the world urbanized enough to have sidewalks and access points. The process
rather recalls the explosive spread of heraldry in the medieval Europe of
the 1120s. There is a site that explains the symbology ;.

