A lawmaker has asked the Federal Trade Commission to investigate online ad companies that track consumers across devices, like showing them ads on their phones based on Web sites they visit on a computer.
The letter, sent on Thursday by Senator Edward J. Markey, Democrat of Massachusetts, to Edith Ramirez, the commission's chairwoman, cited a New York Times article that ran on Sunday detailing the new ways that mobile advertisers are tracking consumers, including across devices.
“Such tracking envelops users in a digital environment where marketers know their preferences and personal information no matter which device they use while consumers are kept largely in the dark,†Mr. Markey wrote.
One of the new challenges for advertisers is that apps on mobile phones do not use cookies, the predominant method for tracking people across Web sites. It has generally been impossible for advertisers to show someone a mobile ad based on searches they did on a different device, for instance, or to know whether a mobile ad resulted in a purchase on another device.
Various companies are figuring out ways to connect people's behavior across devices and show them ads accordingly. One of the companies featured in the article, Drawbridge, applies statistical modeling to data from ad exchanges and Web publishers to determine that several devices belong to the same person.
A Drawbridge spokesman did not immediately respond to a request for comment.
Other companies, like Google, Facebook and Amazon, have other ways to track people's behavior across devices, like when they are logged in to their accounts with those services.
“Previous tracking technologies such as cookies are giving way to more sophisticated, surreptitious methods for monitoring users,†Mr. Markey wrote. “The implications of this evolution are enormous for the privacy of millions of Americans.â€
