Over the past several years, investigations by the Internal Revenue Service and U.S. Justice Department have used the threat of criminal prosecution and financial sanctions to pressure UBS Group AG and Credit Suisse Group AG to pay fines and turn over the names of thousands of depositors. Diplomatic pressure persuaded the Swiss government to enact stricter reporting regulations. DRUG CARTELS The HSBC leak began as a rogue operation by a computer technician, Herve Falciani, who left the company in 2008 with five disks of confidential information. A self-described whistle-blower, Falciani provided details on the 100,000-plus accounts to French Finance Minister Christine Lagarde, now head of the International Monetary Fund. She passed details from the cache—which came to be known as the Falciani List or Lagarde List—to governments around the world.