When you're out and about with your Wi-Fi turned on, you're actually broadcasting your MAC address to retailers, government agencies, marketing agencies and more -- even if you never connect to the wireless network. Firms can use that unique MAC address, along with video surveillance footage to learn your shopping habits and effectively track your location while you're in the range of the basestation.
With iOS 8, Apple now randomizes/spoofs your MAC address while you broadcast your Wi-Fi signal, disguising you from marketers and other firms as they are unable to tell who is who. Once you connect to a wireless network, then your device provides the real MAC address.
That means that companies and agencies that collect such information will not necessarily know when the same device (i.e., person) visits a store twice, or that the same device pops up in stores across the country or the world, suggesting a much-travelled owner.
Thanks to Apple, the practice of Wi-Fi sniffing could now be rendered useless with the introduction of iOS 8.
Read More via Quartz via TheVerge