How your mobile carrier makes money off some of your most sensitive data

T-Mobile says it will use its customers’ web browsing and app usage data to sell targeted ads unless those customers opt out. It sounds very creepy.  But it’s also a good example of just how much of our data can be and is collected through our mobile devices and how few rules there are for the carriers we’re forced to trust with it. Mobile carriers figured out a long time ago that they have two ways of making money off of their customers: what those customers pay to use their services, and then, what carriers earn by selling the data those paying customers provide as they use those services. The latter is buried under lengthy and confusing privacy policies and account settings, and most customers don’t even know it’s happening. There is a little bright spot here: These companies claim that they don’t attach your personal information, like your real name or address, to this data. They either just lump you in with a large anonymous pool of customers to use as aggregate data, or they assign a unique identifier to you, attach a bunch of categories based on interests or demographic information inferred from your data to that identifier, and then give that to third-party advertisers to target their ads to. That’s supposed to prevent advertisers from knowing your real identity, but depending on what’s used as an identifier and how specific the data attached to that identifier is, it could be easy enough to re-identify you through it. You just have to trust that T-Mobile (or Verizon or AT&T) and their advertising partners won’t do that.