Consumer Federation of California

You may have even less privacy than you thought.

Most Internet users know that Web sites and advertisers monitor what they do online and use that information to pitch products and services. What’s not as well known is that these companies can track individuals as they move between devices like personal computers, cellphones and tablets. This type of “cross-device” tracking raises significant privacy concerns because most users are simply unaware that it is taking place.

Internet companies capable of such monitoring do it through various means, including by figuring out if different devices are using the same Internet connection and are visiting the same Web sites and mobile apps. If, for instance, you have used your home computer to research a Hawaiian vacation, travel companies can show you ads for flights to Honolulu on apps you use on your cellphone.

Internet businesses argue that such targeting benefits everybody: advertisers get access to customers who are more likely to buy their products while individuals receive offers for stuff they are interested in. (The New York Times’s mobile apps include software from advertising networks that gather nonpersonal information about how readers use the newspaper.)

But there’s also a big privacy issue. Many Americans worry that the Internet has already extracted more personal information about them they would like. Now comes the news that advertisers can follow people from work computer to tablet computer to cellphone even though those devices are not connected to one another. New technology also allows advertisers access to mobile phones without the “cookies” they need to access personal computers. This makes it harder than ever for users to escape the gaze of private companies.

By connecting information from these devices, database companies that collect information can know a lot more about individuals than previously thought possible, including, for instance, their physical location and the identity of family members, friends and colleagues. The use of this information to target advertising might amount to a mere annoyance to most people. But such information could also end up in detailed individual profiles that could be obtained by government agencies or purchased by employers or banks to evaluate candidates for jobs or loans.

At some point, the makers of computers, phones and software may devise new tools that allow people to protect themselves from sophisticated forms of tracking. But they will always be one step behind firms that are in the business of collecting information.

The best solution is for lawmakers to pass legislation that sets clear rules that would regulate and limit how businesses collect personal information, what they can use it for and how long they keep it. The rules, which could be enforced by the Federal Trade Commission, should also give consumers an easy way to review files about themselves or simply choose not to have the information collected. At the moment, the advantage on the Internet lies increasingly with the data miners and the advertisers, not the consumer.