It will be interesting to see if one day a cyber-attack can be declared as an attack on the country worthy of a military response considering the ramifications of disabling key national infrastructure such as nuclear power plants:

South Korea has obtained first-hand information about the North Korea Cyber War efforts from North Korean Cyber Warriors who have fled south. The defectors report that, in the last few years, there have been a lot of changes in the North Korean Cyber War community. There are now two “hacker brigades” in the North Korean electronic warfare section of the armed forces. Each brigade contains about 600 Internet experts. These hackers have been trained at Pyongyang Automation University, Amrokgang College of Military Engineering, the National Defense University, the Air Force Academy and the Naval Academy. But the Pyongyang Automation University has been the main source of expert hackers. Until recently this place was known as Mirim University (and, not long ago, Mirim College). But the success of Mirim kept the money, expansions and name changes coming.The North Korean hackers have been increasingly busy, and effective. Earlier this year, South Korean network security and intelligence officials revealed that North Korea has been seeking details of how computer systems in key South Korean industries work. Particularly alarming was the effort to find out about the systems that run South Korea’s nuclear power plants (which produce over a third of the nation’s electricity). These systems are not connected to the Internet, but the North Koreans are apparently planning to get an agent working inside a plant, and use a USB stick to plant a damaging bit of software. The North Koreans have also been seeking details about software that runs the stock markets,high-speed rail trains, air traffic control and natural gas distribution systems. Air traffic control is also not connected to the Internet, but its software and facilities are also getting scrutinized by North Korean agents.  [Strategy Page]

You can read more at the link.

News such as this makes you wonder if the Chinese had anything to do with training these hackers?  It seems to me it would be in the interest of the Chinese to use North Korean hackers to test various methods to exploit western cyber-security capabilities without having to do it themselves thus giving the Chinese government plausible deniability.