But here's the irony: According to Mayer, while Turn recreates deleted tracking cookies for Verizon customers using the UIDHs, it doesn't do the same for opt-out cookies if those were set and later removed by those users.
"Clearing your cookies is not the way to opt-out of tailored advertising, and may in fact be counterproductive if you've cleared the cookie that indicates you have opted-out," Ochoa said. "That choice would then be erased and would need to be re-expressed."
Verizon also allows subscribers to opt out of its Relevant Mobile Advertising (RMA) and Verizon Selects programs that use the UIDH. However, those settings just stop Verizon from sharing data associated with those user headers with advertising partners.
The UIDHs are still injected into Web requests and can still be used for tracking or respawning cookies by companies like Turn or even those that are not members of the Network Advertising Initiative (NAI) and Digital Advertising Alliance (DAA).
"So, what's a Verizon subscriber to do?," Mayer said. "Ad blocking would be effective, but it isn't supported by the stock Android or iOS browsers. Using a VPN or other secure proxy would work, though that's quite cumbersome. For an ordinary user, there simply is no defense."
"It is clear that Verizon does not understand the privacy risks it is imposing on its customers," advocacy group the Electronic Frontier Foundation said in a blog post. "The UIDH program should be shut down today. Going forward, the company should undertake to obtain genuine prior, informed consent for any future tracking activities."
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