Elon Musk's control of a federal payment system is raising concerns about funding for programs like Social Security and the safety of personal data.

Elon Musk and his aides have taken control of the US Treasury Department's payments system -- which manages trillions of dollars of transactions each year -- sparking alarm among critics. The Treasury's closely guarded payments system handles the money flow of the US government,

Trump insists that anything Musk does must first be approved by the president.