I Know Where You've Been: Geo-Inference Attacks Via the Browser Cache

Many websites customize their services according to different geo-locations of users, to provide more relevant content and better responsiveness, including Google, Craigslist, etc. Recently, mobile devices further allow web applications to directly read users' geo-location information from GPS sensors. However, if such websites leave location-sensitive content in the browser cache, other sites can sniff users' geo-locations by utilizing timing side-channels. In this paper, the authors demonstrate that such geo-location leakage channels are widely open in popular web applications today, including 62% of Alexa top 100 websites.