The Pentagon has concluded that computer sabotage coming from another country can constitute an act of war, opening the door for the U.S. to respond using traditional military force.

Pentagon officials believe the most sophisticated computer attacks require the resources of a government. For instance, the weapons used in an assault such as taking down a power grid would likely have been developed with state support.

Defense officials refuse to discuss potential cyber adversaries, although military and intelligence officials say they have identified previous attacks originating in Russia and China.