re: What should US do if Russia crashes US computer network?

It would certainly be an act of war. Anything that disrupts our economy (intentionally of course) should be considered as such.

What if NK, Russia and China all joined in the festivities collectively? If you notice, there is a severe trend that people are 'stepping up' to us - terrorists, Russia, China to an extent, petrodollars in other currencies. People that don't think these have serious implications are nuts.