Odds are that you are reading a smartphone screen right now, or at least have a smartphone nearby. The devices are ever-present, which makes them a huge potential source of information about you.
On phones running Google's Android software or Apple iPhones, the privacy options are buried under several menus. One setting can limit how ads are targeted in the apps you use, while another controls the ways your location is tracked throughout the day.
"Based on the signal strength of your cellphone and the different tower, your cellphone is able to see where you are down to a couple of feet," explains Steve Beaty, security engineer at the National Center for Atmospheric Research.
Location settings are particularly confusing because Global Positioning Satellites, cellphone towers and WiFi Internet networks can all be used to determine your location. Adding to the complication on Android phones, the GPS and cell or WiFi tracking are turned off with separate switches.
But physical location isn't the only way your activities are being tracked.