Hacking Everything

I've been thinking about this a lot lately, and I totally believe that there's some super hacker out there ready to take down the technological world with the push of a button. I mean, people are smart, and computers do almost everything these days, I'm sure they're all connected somehow. Especially with all of these wireless networks.

I completely lack the ability to do anything close to this, but where would you start? Maybe try hacking into NASA and tilt all of the satellites just enough that we can't use our cell phones anymore? Then hack into power plants? 

I've been coming up with different scenarios for the collapse of civilization, and this one really intrigued me because I have such little knowledge on it all.

How would you destroy our civilization?