writes "CNN has revealed that there was a test performed in March 2007 where the Department of Homeland Security evaluated what a cyber attack could do against a power plant. The attackers in the classified test were able to take control of the plant's control software and modify the settings of a large generator to the point where it self-destructed. The story relates that until then, they had always believed that the worst that could happen was that attackers would be able to turn something off. An economist looked at a scenario where a third of the US was without power for three months due to destroyed power plant equipment and put a price tag on the massive attack at 700 billion dollars.
They have been working on fixing the vulnerabilities that they found at power plants across the country, but how many other plant control systems need to be fixed? Is it possible to look at severing all computer connections between plant control systems and all other networks and expect them to still function?"Link to Original Source