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.

The company, called 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.