AT&T Chicago store (interior 001)

AT&T told the Associated Press on Friday that it is no longer using permanent cookies to track its subscribers. In late October, security researchers discovered that the carrier, along with its competitor Verizon, were using unique identifying numbers or “perma-cookies” to track their customers online habits.

A spokesperson for AT&T said that the tracking practice was part of a pilot program to improve targeted marketing called “Relevant Advertising.” But it says that the experiment is over, and it has pulled the identifying numbers from their customers’ accounts, although it may still sell the data it’s collected.

Verizon Wireless spokeswoman Debra Lewis told the AP that “as with any program, we’re constantly evaluating, and this is no different,” indicating that it is still tracking customers. She adds that business and government customers are not being tracked, and customers can opt out of the program at anytime.

User privacy on the Internet has become a hot button issue in both politics and technology in recent years. Following Edward Snowden’s leak of the PRISM program slides, several reports have come out regarding the unlawful tracking of users—including one this week on DOJ-run, aircraft-mounted spy boxes.

Verizon customers are able to disable to opt-out of the tracking service using a form on its website, but that won’t stop their identifying code from being inserted in the URL of websites they visit. Users who want to check to see if they are being tracked by their carrier can visit this website from their mobile device.

[Associated Press]