May 29, 2022

Privacy: “Zombie Cookie: The Tracking Cookie That You Can’t Kill”

UPDATE: Zombie Cookies Slated to be Killed (via ProPublica)

NOTE: We’ve updated this post with additional info and a response to the article by

From ProPublica:

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.


Turn’s zombie cookie comes amid a controversy about a new form of tracking the telecom industry has deployed to shadow mobile phone users. Last year, Verizon and AT&T users noticed their carriers were inserting a tracking number into all the Web traffic that transmits from a users’ phone – even if the user has tried to opt out.


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.

Read the Complete Article

UPDATE Jan 15, 2014: How Verizon and Turn Defeat Browser Privacy Protections (via EFF)

UPDATE Jan 15, 2014: In Response to ProPublica

See Also: The Turn-Verizon Zombie Cookie (by Jonathan Mayer, via Web Policy Blog)

See Also: Privacy: It’s Time for the Library Community To Speak Up About Verizon and AT&T Use of X-UIDH Header to Track Wireless Web Users (November 5, 2014)

See Also: Learn More About Turn (via

See Also: Turn on Twitter

About Gary Price

Gary Price ( is a librarian, writer, consultant, and frequent conference speaker based in the Washington D.C. metro area. Before launching INFOdocket, Price and Shirl Kennedy were the founders and senior editors at ResourceShelf and DocuTicker for 10 years. From 2006-2009 he was Director of Online Information Services at, and is currently a contributing editor at Search Engine Land.