Did you ever wonder what those “Free Public WiFi” adhoc networks you see almost every place people use laptops? David Pogue explains it. A stupid Windows bug that acts like a virus but it really isn’t a virus.
The original article goes into more detail:
If a laptop connects to an ad-hoc network it can later start
beaconing the ad-hoc network’s SSID as its own ad-hoc network without the
laptop owner’s knowledge. This can allow an attacker to attach to the laptop
as a prelude to further attack.
This is basically a configuration error that spreads virus-like from laptop to laptop. In field tests, numerous ad-hoc SSIDs such as “linksys”, “dlink”,
“tmobile”, “hpsetup”, and others have been documented.
In other words, if a Windows laptop connects to such a network, it will start advertising the same network name without the owner’s knowledge.