“Our phone is going around the city asking, ‘Are you ‘Home Wi-fi’? Are you ‘Home Wi-fi’?’ Your phone does that one network at a time but it always sends out its MAC address and the name of the network,” Briz continued. “So then it might be like, ‘Hey, it’s me. Here’s my MAC address again. Now I’m looking for ‘Work Wi-fi’, now that cafe I connected to once, now ‘Mom’s House’, and so on.’” The protocol is structured like a Greek tragedy, with recurrent choral interjections and a relentless quest for home.
Many people think that you need GPS to be able to locate a device. This article explains very nicely why WiFi alone is a very capable tracking technology if you are walking around with a smartphone all day – and why this huge privacy issue is very unlikely to go away.