Strategypage writes that actual killing is contemplated against virtual attackers:
Crime, and warfare, over the Internet is getting more dangerous for the attackers. Internet security experts are now doing to hackers what hackers have been doing for years; finding flaws in their software and exploiting it. This makes it possible to counterattack and, more importantly, identify, locate and arrest criminal hackers. For military ones, you could obtain GPS coordinates, enabling you to send a "cease and desist" message in the form of smart bombs.
Blowing them to bits may not be as elegant as cyber warfare aimed back at them, but it is very binary, no? They're either alive or dead, and the dead don't hack.