Just like out of the movies. Security holes in the software that controls power plants, water supplies, etc, running on systems that are connected to the Internet. Buffer overflows, even. I'm scared.
But it gets worse:
Why are these things running Windows‽ (I'm assuming, given how many Mac/Linux worm problems there have been...)What's clear is that such control systems are increasingly vulnerable to Internet-borne threats, since viruses and worms have disrupted service in power plants, automobile factories and gasoline pipelines - even when those facilities weren't targeted.