A group of Democratic US senators on Tuesday demanded Yahoo Inc explain why hackers' theft of user information for half a billion accounts two years ago only came to light last week and lambasted its handling of the breach as "unacceptable."
The lawmakers said they were "disturbed" the 2014 intrusion, disclosed by the company on Thursday, was detected so long after the hack occurred.
"That means millions of Americans' data may have been compromised for two years," the senators wrote in a joint letter addressed to Yahoo Chief Executive Officer Marissa Mayer.
"This is unacceptable." Yahoo did not immediately respond to a request for comment about the letter, which was signed by Senators Patrick Leahy, Al Franken, Elizabeth Warren, Richard Blumenthal, Ron Wyden and Edward Markey.