Despite its enticing name, the network, available in thousands of locations across the United States, does not actually provide access to the Internet. But like a virus, it has spread — and may even be lurking on your computer right now.
Wireless security expert Joshua Wright first noticed it about four years ago at an airport.
"I went to connect to an available wireless network and I saw this option, Free Public WiFi," he remembers. "As I looked more and more, I saw this in more and more locations. And I was aware from my job and analysis in the field that this wasn't a sanctioned, provisioned wireless network, but it was actually something rogue."
Free Public WiFi isn't set up like most wireless networks people use to get to the Internet. Instead, it's an "ad hoc" network — meaning when a user selects it, he or she isn't connecting to a router or hot spot, but rather directly to someone else's computer in the area.
Though it doesn't actually provide Internet access, the network has spread across the country thanks to an old Windows XP bug.