So you walk into a cafe and settle down with your dessert. You turn on the wi-fi on your phone and you find this Free Public WiFi network. Should you join it?

You connect to it and nothing happens. I mean you can’t browse at all. It is like you are connecting to a WiFi router  that is turned on but has no connection to the internet.

What is this mysterious network that is everywhere. You can find it in airports, cafes etc. And you can never connect to the internet via it.

The answer is actually a funny bug with older versions of Windows XP (pre SP3). Let’s say we have a computer AA in Bangkok airport that is running an older version of Win XP.  AA can’t find the regular network it connects to, it creates its own ad hoc network. The WinXP names this network after the  last  wi-fi point it connected to. Now imagine another notebook BB running an older version of Windows is in the vicinity and it is trying to connect to a network. BB finds the network that AA is broadcasting. Now BB is connected to AA’s network. imagine now that  the owner of BB took a flight to Hong Kong. At Hong Kong airport, notebook BB is turned on and it can’t find any network. Computer BB will now start broadcasting a network. The name of this network will be the same as the the network it connected to earlier in Bangkok. In this way this “zombie” network continues spreading throughout the world with computers running older versions of XP as its host.  What must have happened is someone, somewhere created a network with the name “Free Public WiFi”. Many people tried to connect to it and unknowingly they just kept spreading this network name around the world.

This Free Public Wi-Fi network is harmless. As all you do is connect to a computer. But there might be some naughty people purposely running a network with this name to try to get people to connect to it. It is possible to spy on your data this way. So even if you see this network, don’t join it. Avoid joining any public wi-fi network that you are not sure of. Also, if you see this “Free Public WiFi” network at your home or office, it means that there is an un-patched Windows XP computer somewhere. Try to find it and apply updates to it.

I found out about this at http://www.npr.org/2010/10/09/130451369/the-zombie-network-beware-free-public-wifi