substations serving iran's power grid. >> we have now had a cyberattack that was disruptive. a power outage impacts everything. from air traffic control to sub ways traffic lights, water, and food supplies. cnn was given rare access to a government test facility in idaho falls. >> is it difficult for a cyber attacker to take down a power grid. >> it is much more simple than we would like it to be. >> to show us how simple, they recreated the ukraine attack.