The new model of Internet advertising scares the heck out of us. It's called behavioral targeting. What that amounts to, in a nutshell, is following you around the web from site to site recording your movements and using that record to sell you personalized ads. All those ads that pop up on the side of articles on your favorite websites like ESPN.com or NYTimes.com are often not provided by those sites, they are from third parties that you've never heard of, with names like Lotame Solutions Inc. Using a variety of techniques, those companies are tracking where you go throughout the web.

Some advertisers like this because they can charge a premium for this personalization. For example, when someone visits an automotive website, knowing his or her income level allows the advertiser will know whether to highlight a Subaru or a Range Rover. According to one online advertising CEO's statement "[m]oving from site-targeting to people-targeting is the central dynamic of the industry". But the inevitable byproduct of all of this tracking is the creation of an extremely detailed profile on all of us — what we read, what we do and where we go online. And this information is not anonymous. Using clues — from pages we log into or visits to our profiles on social networking sites — we reveal our identity.

Worst of all, these online profiles do not stay with the advertisers. They are merged with "offline content," namely the information that advertisers, background check companies and data aggregators have been collecting on us for years. All of these companies have contracts with employers and the government. One company boasts it's "the silent partner to municipal, county, state, and federal justice agencies who access our databases every day to locate subjects, develop background information, secure information from a cellular or unlisted number, and much more."

To boil it down: private companies are tracking all our movements online, selling that information to other companies who in turn share it with law enforcement and the government.

Wow.

As this practice spreads, the chilling effect on our First and Fourth Amendment rights will be immense.

So what do we do about it? We have to break this new surveillance model at the source — with the advertisers who are collecting all this information. One of the best ways to do that is to give everyone a universal way to opt-out of tracking, specifically a "Do Not Track" list. Modeled on the popular "Do Not Call" registry, people would visit a central site overseen by the government where they could register their desire not to have their online movements tracked. While a number of technical details have to be worked out, such a mechanism represents the best way to short-circuit this new type of private spying before it can forever alter the Internet and our freedoms.

To learn more, read the ACLU's comments to the administration on how it can better protect online privacy. A good start would be an update to the Electronic Communications Privacy Act (ECPA): Tell Congress you demand a privacy upgrade!

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