How to See If AT&T, Verizon Track You Online

Another day brings another new way for companies to track you online without your permission. This time, the culprit is AT&T, and the method is an extremely complex tracking cookie. The mobile carrier is, in all likelihood, currently in the process of testing a system that can track your online activities in order to sell data to advertisers.

You don't have to take my word for it, either; you can test for yourself in a mobile Web browser. Kenn White, an independent security researcher, provided a process to let users test their phones a few days ago when it came to his attention that Verizon Wireless was already doing the same thing as AT&T. As long as you're connected to a carrier's 4G or 3G network, the carrier can monitor which sites you visit and how long you spend on each one.

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Forbes corresponded with AT&T on the matter as well. While the carrier would not confirm exactly what it was working on, it did say that it was testing something, and that it was considering a "mobile Relevant Advertising program." Those assertions are consistent with the kind of tracking cookie White found while testing AT&T's network.

AT&T made clear to Forbes that if it implemented such a code, customers would be able to opt out of the functionality and that a customer's unique code would change every 24 hours, making him or her impossible to identify. Verizon Wireless claims the same thing. As things currently stand, researchers have found that AT&T has used the same codes repeatedly over multiple days, and still tracking customers who opted out (although presumably no longer sharing the data with advertisers).

It's worth noting that although White has proven the existence of these cookies only on Verizon Wireless and AT&T, he has noticed that similar cookies appear on T-Mobile. If these three companies use them, Sprint may not be too far behind.

Verizon and AT&T are probably not doing anything too insidious with your data, but advertisers really want to know who you are and what you're looking at, and the mobile carriers seem all too happy to provide that information. Verizon Wireless provides instructions for how to opt out of the program on its website, whereas AT&T users will not have that option until the company announces it officially.

Marshall Honorof is a Staff Writer for Tom's Guide. Contact him at Follow him @marshallhonorof and on Google+. Follow us @tomsguide, on Facebook and on Google+.

Marshall Honorof

Marshall Honorof is a senior editor for Tom's Guide, overseeing the site's coverage of gaming hardware and software. He comes from a science writing background, having studied paleomammalogy, biological anthropology, and the history of science and technology. After hours, you can find him practicing taekwondo or doing deep dives on classic sci-fi.