WASHINGTON (AP) -- AT&T Mobility says it's no longer attaching hidden Internet tracking codes to data transmitted from its smartphones.

That practice made it nearly impossible to shield its subscribers' identities online. AT&T said the effort was part of a test and had passed the code along to websites that a user visited.

On the phone, hands-free. (AP Photo/Gregory Bull, File)

But Verizon Wireless, the country's largest mobile firm, said Friday it still uses this type of tracking.

Those tracking codes are part of the latest plan by the cellular industry to keep tabs on consumers and their devices. The codes don't explicitly contain personal information but they're unique sent to websites alongside personal details.

Consumers' interest in privacy and their digital anonymity has intensified in recent years following revelations by former National Security Agency analyst Edward Snowden.

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