This sounds right:
The Pentagon has concluded that computer sabotage coming from another country can constitute an act of war, a finding that for the first time opens the door for the U.S. to respond using traditional military force.
Whether this matters is another question. We brush off acts of war nearly every day because it is politically inconvenient to recognize them, so I think the deterrent effect of this finding will be limited.
(Via Volokh.)
Internet Scofflaw 