The U.S. government spent more than a decade preparing responses to malicious hacking by a foreign power but had no clear strategy when Russia launched a disinformation campaign over the internet during the U.S. election campaign, current and former White House cybersecurity advisers said.

Far more effort has gone into plotting offensive hacking and preparing defenses against the less probable but more dramatic damage from electronic assaults on the power grid, financial system or direct manipulation of voting machines.

Over the last several years, U.S. intelligence agencies tracked Russia's use of coordinated hacking and disinformation in Ukraine and elsewhere, the advisers and intelligence experts said, but there was little sustained, high-level government conversation about the risk of the propaganda coming to the United States.