The first time Scott Lunsford offered to hack into a nuclear power station, he was told it would be impossible. There was no way, the plant’s owners claimed, that their critical components could be accessed from the Internet. Lunsford, a researcher for IBM’s Internet Security Systems, found otherwise. “It turned out to be one of the easiest penetration tests I’d ever done,” he says. “By the first day, we had penetrated the network. Within a week, we were controlling a nuclear power plant. I thought, ‘Gosh. This is a big problem.'”
http://www.forbes.com/technology/2007/08/22/scada-hackers-infrastructure-tech-security-cx_ag_0822hack.html