Sony shares fell 2 percent on news of the potentially huge data leak, ending Wednesday trading in Tokyo at 2,366 yen, down 49 yen.

A class-action lawsuit was filed in the U.S. accusing Sony of not taking "reasonable care to protect, encrypt and secure the private and sensitive data of its users." It seeks monetary compensation and free credit card monitoring.

Sony that clarified credit card information was stored in an encrypted form and added, "we have no evidence that credit card data was taken." Other personal information was not encrypted.

Thursday, April 28