The original question was how to make cyber war lethal. I even addressed issues with a military-only option before the question change. It is my belief that cyberwarfare will not be clean or tidy. Once it starts, civilians will die.
- Shut down all computers in hospitals
- Shut down all air traffic control systems
- Shut down all banking systems
You could skip the first steps, but if you could do coordinated attacks, all of these systems usually have their own backup power. You could try and order a full scale attack with the military and hope the retaliation wipes out the country. There's enough protections in place that this would most likely not work. But if you're looking for scenarios, it's a great one. Don't turn our military on our civilians, turn another military into the attacker.
- Shut down the electrical grid
Chaos will rear it's head and do the follow-up work for you. With no power, many industries stop working. With so much emphasis on electronic currency, most countries would fail to be able to function in a normal fashion.
I bet the ppeppers are the first to go. ;)
Good luck with anarchy.