Invasion of Cyber Crime: CNBC— Code Wars: America's Cyber Threat

On August 14, 2003 there were massive power blackout in Northeast, most prominently affecting New York and Toronto. One hundred power plants shut off, phone lines and water lines were down and people were trapped in elevators. Just a few days before in Toronto and computer virus known as blaster had infected airline and train technology, delaying their departure for many hours. The officials claimed that blaster was not the official cause of the largest blackout in American history that totaled no less than 60 billion dollars of damage. The official cause was overgrown trees and brush on power lines. However, virus hunter Mikko Hypponen disagrees. According to the report, the screens flashed black screens and described everything that would be the cause of blaster. As blaster is a worm, it doesn't need programs to propel itself on the net. Your computer could get a worm by being online, like the financial network, power plants, water treatment centers and nuclear reactors. As most people disagreed with the official report it was a wake-up call: computer viruses could impact the physical world.

Example of how a blaster worm works.
http://www.cisco.com/web/about/security/images/mysdn/mysdnimage005.gif

Web Warriors - CBS Documentary (full episode)