Verizon users might want to start looking for another provider. In an effort to better serve advertisers, Verizon Wireless has been silently modifying its users’ web traffic on its network to inject a cookie-like tracker. This tracker, included in an HTTP header called X-UIDH, is sent to every unencrypted website a Verizon customer visits from a mobile device. It allows third-party advertisers and websites to assemble a deep, permanent profile of visitors’ web browsing habits without their consent.
Verizon apparently created this mechanism to expand their advertising programs, but it has privacy implications far beyond those programs. In fact, it apparently allows others to find out about Verizon users.
Full details may be found in an article by Jacob Hoffman-Andrews in the Electronic Frontier Foundation’s web site at https://www.eff.org/deeplinks/2014/11/verizon-x-uidh.