Warchalking is the practice of marking a series of symbols on sidewalks and walls to indicate nearby wireless access. That way, other computer users can pop open their laptops and connect to the Internet wirelessly. It was inspired by the practice of hobos during the Great Depression to use chalk marks to indicate which homes were friendly.
warchalking.org
craiefiti (in french)
[c bien, ca rajoute encore des choses sur les murs apres les tags et les stickers, je prefere voir ca que des pubs avec des femmes denudees]