Friday, January 16, 2015

Zombie Cookie: The Tracking Cookie That You Can’t Kill

ProPublica reports Zombie Cookie: The Tracking Cookie That You Can’t Kill "An online advertising clearinghouse relied on by Google, Yahoo and Facebook is using controversial cookies that come back from the dead to track the web surfing of Verizon customers."

"In November, AT&T stopped using the number. But Verizon did not, instead assuring users on its website that "it is unlikely that sites and ad entities will attempt to build customer profiles" using its identifiers."

Um, don't sites and ad entities explicitly want to build customer profiles to provide relevant ads?

It works like this: When a user visits a website that contains Turn tracking code, the company holds an auction within milliseconds for advertisers to target that user. The highest bidder's ad instantly appears on the user's screen as the web page loads. Turn says it receives 2 million requests for online advertising placements per second.

For its auctions to work, Turn needs to identify web users by cookies, which are small text files that are stored on their computers. The cookies allow Turn to identify a user's web browsing habits, such as an interest in sports or shopping, which it uses to lure advertisers to the auction.

Some users try to block such tracking by turning off or deleting cookies. But Turn says that when users clear their cookies, it does not consider that a signal that users want to opt out from being tracked.

The idea of advertisers trying to know me to give me relevant ads actually doesn't bother me too much. What does is that that same system can be used by others for purposes I might not approve of. E.g., the NSA tracking all my surfing, thieves tracking my purchases and location (when I'm not home), etc.

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