Selling You As Data [MUSIC PLAYING] The most detailed documenting of our lives is done by technology companies. Two years ago, tech researcher Julia Angwin decided to investigate how much these companies track our behavior daily. Her findings give us one of the best pictures yet of just who is watching us online, every minute of every day. JULIA ANGWIN: When I talk about the underbelly of the information revolution, I'm really talking about the unseen downside of the information revolution. You know, we obviously have seen all the benefits of having all this information at our fingertips. But we're just awakening to the fact that we're also being surveilled all the time. We're being monitored in ways that were never before possible. [MUSIC PLAYING] Every time we browse the internet, what we do can be collated and sold to advertisers. So basically, online there are hundreds of companies that sort of install invisible tracking technology on websites. [MUSIC PLAYING] They've installed basically a serial number on your computer, and they watch you whenever they see you across the web, and build a dossier about your reading habits, your shopping habits, whatever they can obtain. And then there's a real market for that data. They buy and sell it, and there's an online auction bidding for information about you. And so the people who know your browsing habits can also discover your deepest secrets, and then sell them to the highest bidder. So let's say a woman takes a pregnancy test and finds out she is pregnant. Then she might go look for something online. By making pregnancy-related searches, this woman has become a hot property for the people looking for a good target for advertising. The process of selling then begins. Within seconds, she is identified by the companies watching her. Her profile is now sold multiple times. She will then find herself bombarded with ads relating to pregnancy. JULIA ANGWIN: She may well find that she'll be followed around the web by those-- by ads. And that's really a result of that auction house. Now, they will say to you that they know who-- they know she's pregnant, but they don't know her name. But what's happening is now that, more and more, that information is really not that anonymous. You know, it's sort of like if they know you're pregnant and they know where you live, yes, maybe they don't know your name, that's just because they haven't bothered to look it up. We continually create new information about ourselves. And this information gives a continual window into our behaviors and habits.