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

Turn, 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.

Turn is taking advantage of a hidden undeletable number that Verizon uses to monitor customers' habits on their smartphones and tablets. Turn uses the Verizon number to respawn tracking cookies that users have deleted. 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.