a report shows the mill was hacked through bobby trapped emails, giving hackers access to the system. part of the plant failed, including a furnace that could not be shut down as normal. >> the attack on the steal meal was interesting. there's a few countries in the world that have the capability to do this kind of attack, right. only a handful of countries could do something like that. but it is frightening, because they were able to get into the control systems for the steel mill and damage them, causing physical damage. this is an example of what a terrorists. >> reporter: cyber warfare can be conducted remotely and anonymous as demand. >> we didn't have a p.s.v., we caused is pipe rupture in the process. usingcm at u.s. gat facilities, hackers showed how easy it was. causing the pipes to explode and overflow. >> for the demonstration it was filled with water. >> when the isolation volve is pump. >> it didn't happen. out. >> there has been 79 hacking attacks against u.s. energy companies, investigated by the computer emergency team. a division of the department of homeland security