Learn who’s following your online habits and what you can do about it.

By Abigail Pesta
Updated March 06, 2014
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Illo: person being watched by computer
Credit: Papercut.fr

You clicked on a coveted pair of pumps while surfing the Web, and now those shoes are popping up in ads on your social-media pages, in your e-mail, just about everywhere. You can’t shake them because you’re being tracked. With every move you make on the Internet, sophisticated technology collects data on you, and that information gets used for targeted marketing campaigns. The trend is undoubtedly a little disturbing, but is it something that should worry a regular consumer? Julia Angwin, the senior technology and privacy reporter at ProPublica and the author of a new book on Internet privacy, Dragnet Nation: A Quest for Privacy, Security, and Freedom in a World of Relentless Surveillance ($28, amazon.com) gives us her take.

Who is doing the tracking?

Social-media sites, cell-phone companies, e-mail services, cell-phone apps, online retailers, and search engines are all collecting comprehensive dossiers on you. Most say that they don’t sell or share information that identifies you by name, but they do admit to using this information to find audiences for specific ads, like the ones that show up on Facebook.

Why should you care?

You don’t know what these personal dossiers could be used for in the future. We have learned from the documents released by Edward Snowden that the National Security Agency is scooping up information from companies that collect data on people. That data can be used for a number of things. In addition, commercial tracking could eventually mean individualized prices for everyone. This is already starting to happen at some online retailers. If you buy an expensive pair of pants, for example, an assumption may be made about you and what you can afford to pay. Higher prices may be tailored to you as a result.

What information is being collected?

Data that you may have entered yourself (say, your address or personal interests), as well as information that you didn’t contribute (like which kind of smartphone you have and the locations that you physically visit while you’re using your phone to browse the Web). The sites you frequent are also fair game. For example, if you’re on Facebook and then, without logging out, you open a new window for a website that has a Facebook “like” button, Facebook will find out that you looked at the website, whether you clicked on the “like” button or not. Generally, any social-media buttons that are designed to share or promote content keep tabs on you. E-mail tracks you, too. Different providers have different methods of doing so. Gmail uses technology to select ads based on what you write. So if you send a note to a friend about taking a cruise, you can expect to soon see ads for vacation packages.

Is there a way to stop tracking from happening?

It helps to log out of social-media sites after each visit; trackers usually can’t find you when you’re logged out. Or you can download free software that blocks Internet tracking tools, like Disconnect [disconnect.me] or Ghostery [ghostery.com]. As for e-mail, some providers do let you opt out of personalized advertisements. Gmail users can do so on the Privacy Policy page. Going forward, you’ll receive generic ads, not individually targeted ones. You can also sign up for a secure e-mail service that doesn’t track you. I use Riseup.net. Unfortunately, because it has a very small storage limit, it’s not for everybody.

Do brick-and-mortar retailers track people, too?

Yes. Some malls and stores have started to use technology that tracks customers’ cell-phone Wi-Fi signals. Shops use the information to see patterns where people are spending—for example, which aisles they gravitate toward—so they can display products accordingly. (Helpful hint: If you turn off Wi-Fi as you browse, the technology won’t be able to find you.) Store-loyalty cards are another tracking device. Companies use the cards to keep a record of what you buy. They can then sell that data to brokers, who may sell access to it to marketers. If you use a store-loyalty card, assume that you’re sacrificing your privacy.