It seems unlikely with the technology I am aware of that combat will come about as a result of a cyber attack. It is just too easy to cover your tracks. For some time I expect serious attention will be payed to making tracing of attackers a surer thing. Until that time good old fashion spy work and a lot of our own hacking will be the way to find perpetrators and barring that leaving tasty little poison pills around to go after the perpetrators information and infrastructure seems likely. The only problem with that is that the bad guys eventually have your poison pill codes and can use it against you on less defended portions of your information structure. We need computers and networks designed from the ground up with security in mind and independent networks that are not connected to the internet for critical infrastructure.

Perhaps there is already technology that can catch the perpetrators of cyber warfare with their hand in the cookie jar. The fact that we are considering this an act of war may suggest it already exists.