Check out Winn Schwartau and some of his topics of discussion about cyberwarfare (Google or You Tube). He was a keynote speaker at AFCOM and drove home some very relevant and serious points about the potential (and current) use of the internet as a means for cyberterrorism.
As someone had asked him before, 'Why would they do something like that?' The answer, 'Because they can!'
http://en.wikipedia.org/wiki/Winn_Schwartau