Does Jeh Johnson consider Russia’s cyber attack against the US to be an act of war?

"When I was at Homeland Security, I used to tell people to prepare and plan for the next attack, not the last attack. I used to try to encourage my people to think aggressively, to try to stay one step ahead of the enemy." Former US Homeland Security Secretary Jeh Johnson spent years trying to protect the United States against the kind of massive cyber attack that Russia carried out against American businesses and government agencies in the last year. But at what point should we view such a breach as more than a remarkable feat of espionage? When does it constitute an act of war?

Johnson's conversation with Ian Bremmer was part of the latest episode of GZERO World, which begins airing nationally in the US on public television Friday, January 8th. Check local listings.