Verizon Wireless injects identifiers that link its users to Web requests

Verizon Wireless is adding cookie-like tokens to Web requests traveling over its network. These tokens are being used to build a detailed picture of users’ interests and to help clients tailor advertisements, according to researchers and Verizon’s own documentation.

The profiling, part of Verizon’s Precision Market Insights division, kicked off more than two years ago and expanded to cover all Verizon Wireless subscribers as part of the company’s Relevant Mobile Advertising service. It appends a per-device token known as the Unique Identifier Header (UIDH) to each Web request sent through its cellular network from a particular mobile device, allowing Verizon to link a website visitor to its own internal profiles. The service aims to allow client websites to target advertising at specific segments of the consumer market.

Privacy experts recently began warning of the issue, arguing that the service is essentially tracking users and that companies paid for a fundamental service should not be using the data for secondary purposes.