AT&T will no longer use ‘supercookies’ to track mobile behavior

AT&T said Friday that it will no longer use hidden, undeletable codes to track mobile users’ online behaviors for marketing purposes, according to the Associated Press.

“It has been phased off our network,” AT&T spokeswoman Emily J. Edmonds told ProPublica.

Known as a “supercookie” or “perma-cookie”, the serial number, which uses a special combination of letters, numbers, and characters, attaches to data sent from a user’s smartphone when he or she visits a website. The code is more robust than a typical browser cookie and cannot be removed in the same way.

The serial number is unique and not connected to a user’s personal data. However, it can inadvertently couple with personal information, when a user enters in something like a name or phone number while visiting a website, which already has been tagged with an identification code.

Codes were being used to map users’ online behaviors in order to better market products based on their tastes. A diagram on Verizon’s Precision Markets website illustrates how the codes work.

Verizon, the nation’s largest wireless company with more than 120 million users according to Strategy Analytics, continues to use supercookies. In its privacy statement, it said that the codes are changed with enough frequency to safeguard a user’s privacy.  and states that the codes are changed to ensure user privacy. Wired magazine reported on Verizon’s participation in October.

At the end of October, ProPublica reported that Twitter was using the Verizon tags to market items to users on social media.

A petition titled “Tell Verizon, Stop Tracking Us on the Web” has over 27,000 signatures.