U.S. says North Korea 'directly responsible' for 'WannaCry' cyber attack

White House Homeland Security Advisor Tom Bossert gives an update on the federal response to Hurricane Irma during the daily news briefing at the White House in Washington, U.S. September 11, 2017. REUTERS/Jonathan Ernst/File Photo

WASHINGTON (Reuters) - North Korea is "directly responsible" for the so-called WannaCry cyber attack that crippled hospitals, banks and other companies across the globe earlier this year, a senior White House official said on Monday.

"The attack was widespread and cost billions, and North Korea is directly responsible," Tom Bossert, the White House homeland security adviser, wrote in an opinion piece published online by the Wall Street Journal.