We have the technology and have even more capability. If any country attaks us from the internet, We should have the ability to protect while we boomerang back at them by shutting of their internet from satelites we already have in place.
That means all ip addresses in that country would be automatically blocked from being able to access anything on the internet anywhere.
The question is:
Why have we not done this?
It is believed we have even further capabilities than just isolating their reach to zero. Send them a new virus at the same time so their computers and servers go down for a long period of time.