In this paper, the authors show that Apple's WPS can be abused to create a privacy threat on a global scale. They present an attack that allows an unprivileged attacker to amass a worldwide snapshot of Wi-Fi BSSID geolocations in only a matter of days. Their attack makes few assumptions, merely exploiting the fact that there are relatively few dense regions of allocated MAC address space. Applying this technique over the course of a year, they learned the precise locations of over 2 billion BSSIDs around the world. The privacy implications of such massive datasets become more stark when taken longitudinally, allowing the attacker to track devices' movements.