THIS IS HOW YOU TAKE A NATION DOWN

Imagine if the grid dropped now.  Most would freeze to death within just a few days (at least right now).  Most cannot handle very basic infrastructure changes.

This is a very real threat.  If you are China, you do not invest millions into the study of the other nation's infrastructure unless you have nefarious plans.

Here is the article:

http://www.cnn.com/2014/11/20/politics/nsa-china-power-grid/index.html