The Viral Non-virus
One of our network techs came by a few hours ago trying to track down a rogue ad-hoc WiFi network (not necessarily an easy task, btw) called "Free Public WiFi". After googling around for a while, I came across this:
In short, some (maybe most) operating systems will hang on to - and re-publish - an ad-hoc SSID long after leaving the original spot where it was picked up, effectively spreading the network uncontrollably as the computer moves around and "infects" other computers. This particular SSID has been seen all over the world, apparently.
Oh, and the guy did find the offending laptop in the end, homing in on it with a signal strength indicator.
We have a similar thing here, at my school. Some of us create an encrypted ad-hoc network when we want to chat, transfer files, etc.
There is now a permanent *unencrypted* ad-hoc network here by the same name.
Also, by most, I think you mean Windows.
A someone near the building of the business i work is broadcasting this network. And it drives me insane. I cant tell you the number of times I had to 'fix' a computer because it was connected to this network, preventing the person from connecting to network drives.
The starbucks on the corner has a wifi signal strong enough to work in my building. People connect to it all the time. PITA.