So, this is sort of delightful and hilarious.

If you travel at all, or take your laptop (or phone, these days) into places that may have a wifi network you can use — airports, hotels, coffeeshops, conference centers, etc. — you’ve seen the everpresent mystery network “Free Public Wifi.” Maybe you’ve even tried to connect to it — I never have, since it looks obviously fake to me, but I have always wondered why it’s there.

Well, NPR has the story. The gist it this:

When a computer running an older version of XP can’t find any of its “favorite” wireless networks, it will automatically create an ad hoc network with the same name as the last one it connected to -– in this case, “Free Public WiFi.” Other computers within range of that new ad hoc network can see it, luring other users to connect.

The hilarious part of this is that the notion of this mythical network has spread based entirely on this bug for years now, but nobody actually knows where the original, valid “Free Public Wifi” network was. It just lives on, a digital zombie, in the memories of a million out-of-date Windows laptops. Here’s a more detailed walkthrough of how the network ID has spread; it really is “viral,” just nondestructive.

Bonus: It’s not the only one. If you see ad-hoc networks out in the wild named things like “dlink” or “linksys,” they’re probably the result of the same bug.