Minor clarification...

The Pentagon will reclassify cyber attacks as an aggressive act if it causes the equivalent loss of life or damage to infrastructure as a conventional military attack
Certainly nobody's going to fire off missiles in retaliation for cyber espionage, any more than they would in retaliation for conventional espionage. Of course the US is doing the same thing to China, but the Chinese don't howl to the press when they find out about it.

Everybody spies on everybody else, with whatever tools are available. This is nothing new.