(AP) AT&T Mobility, the nation’s second-largest cellular provider, said Friday it’s no longer attaching hidden Internet tracking codes to data transmitted from its users’ smartphones. The practice made it nearly impossible to shield its subscribers’ identities online. The change by AT&T essentially removes a hidden string of letters and numbers that are passed along to websites that a consumer visits. It can be used to track subscribers across the Internet, a lucrative data-mining opportunity for advertisers that could still reveal users’ identities based on their browsing habits. Verizon Wireless, the country’s largest mobile firm, said Friday it still uses this type of tracking, known as “super cookies.” Verizon spokeswoman Debra Lewis said business and government customers don’t have the code inserted. There has been no evidence that Sprint and T-Mobile have used such codes.