The nation's power grid was put to the test last week as Homeland Security and 150 other groups simulated cyber attacks and even armed commandos at the nation's nuclear facilities.

Dubbed GridEx II, this was the second such test in as many years.  Results likely won't be made public for several months.

Public Citizen's David Power says the tests are critical as we become more dependent on electronic, internet-based systems.

“This is well choreographed simulation with a massive physical and technical attack on the grid to see what procedures they need to come with, and how quickly they can restore it,” Power tells KTRH News.

“If I want to get my grid back up after a hurricane, I need technology,” he says.  “But that might be inviting problems from another source.

Power says while armed commandos may be unlikely, simple malware uploaded from a USB drive could shut the whole grid down.

“Even having security at a very high-level doesn't mean nobody will get it,” he says.  “It certainly means you won't get some teenagers from somewhere playing games, which has happened in the past.”

A long-term black out could interrupt supplies of water, fuel and food for weeks. Plus, 99-percent of military facilities rely on commercial power.