Amid the buzz in Washington about new North Korean nuclear threats, President Barack Obama late last week summoned 15 of America’s top financial leaders to the White House to discuss what his administration considers to be threats that are more pervasive, more persistent and less manageable ‑ cyber risks.

“The president scared the hell out of all of us, and we’re not easy to frighten,” said one member of the group, which included Goldman Sachs’s Lloyd C. Blankfein, JPMorgan Chase’s Jamie Dimon and Bank of America’s Brian T. Moynihan. “This isn’t like the nuclear threat, where it was really governments facing down governments. The American financial sector is a new battleground, and we’re going to have to invest millions of shareholders’ dollars to protect ourselves from what are essentially national actors.”

In this new world, cyber conflicts have already begun. But no one has written the rules of how they should be managed between government and private-sector responsibility.

Unlike typical national security crises, the private sector controls most of the levers that can decisively resolve cyber conflicts. Government maintains overall responsibility for national cyber defense, yet it hasn’t haven’t developed doctrines of response. Officials remain too constrained by internal processes, competing interests and lack of experience in settling national security problems in collaboration with the private sector.

By coincidence, a few blocks down Pennsylvania Avenue from the White House meeting, a group of leading cyber strategists was engaged in a harrowing simulation that showed why Obama is so worried. It illustrated how quickly a cyber conflict could escalate in coming weeks were tensions with Iran over its nuclear weapons’ ambitions to heighten. The session, convened by the Atlantic Council (of which I am president) and the private company SAIC, demonstrated how government officials and the private sector often fail to communicate effectively or act collaboratively to address a national security threat they can only master together.