“What warchalkers do is go around town with their laptops and search for 802.11x networks which allow free access of bandwidth. Then they make a mark with a chalk so other laptop totting people can just walk by and get connected around that spot and check their email or whatever.
Generally, most 802.11x networks aren’t secured and anybody passing by can easily tap into what people do in those networks. Now, since this is wireless, it’s very tempting for certain people to spy on what’s coming down the unsecured pipeline. A guy sitting in a parked car could be doing it or somebody in the upper floors, etc. Every single thing you do on your PC is out in the open. Nothing alarming though, since most people have nothing valuable, although some basic form of security is what network techies advise, to ward off the clueless who get on the nework by mistake.
But, given anything, a enterprising person can break it using known or obsure unpatched holes in the OS (especially Microsoft Windows). Even if you are sitting safe and secured in your house and conencted by wire (cable/dsl/phone line).”