The Pentagon is in the process of developing a formal policy that would consider a computer attack from another nation against the US an act of war, which would carry military engagement implications.
There has been debate for quite some time that the US response to a computer attack should be found within an array of reprisals including economic sanctions, retaliatory cyberattacks or a military strike.
This new policy does not address how the US will respond to non-nation states conducting cyberattacks against the US or it's inhabitants. One of the clear challenges of this new deterrence policy is the difficulty in accurately and confidently pinning an attack to a nation or non-nation state. Take, for example, the case of Google which pin-pointed the attack to computer servers in China, but the US Government did not formally accuse China as being responsible for the attack--an act that would carry clear political implications.