Senators call for investigation into Verizon 'supercookies' that tracked mobile customers

Democratic senators are calling on federal regulators to investigate Verizon Wireless, the country's biggest mobile provider, for secretly inserting unique tracking codes into the Web traffic of its estimated 100 million customers.

Data privacy experts have accused Verizon of violating consumer privacy by using these "supercookies," an identifying string of letters and numbers that become attached to each site visited on a person's mobile device. Sen. Bill Nelson of Florida, the top Democrat on the Senate Commerce Committee, said he wants to know whether the company violated any laws and whether legislation is needed.

Verizon Wireless spokeswoman Debra Lewis said the company takes customer privacy seriously and will respond to Nelson's letter. The company had announced last week it would allow customers to opt out of the tracking program.