Faces lit only by computer screens, fingers in constant motion on the keyboard, eyes focused. It is a scene unlikely to be found in North Korea, where the Internet is one of the world’s most restricted. Now, security experts in South Korea think otherwise.

South Korea reportedly traced the recent massive shutdown of computer servers to North Korea through a Chinese IP address. Seoul, however, has yet to come up with proof that the intrusion came from Pyongyang. Even so, South Korean experts have been keeping their eyes on their estranged neighbor.

South Korea and the US believe the North Korean regime has trained thousands of “cyber-warriors” to carry out its warfare into cyberspace, according to The Associated Press.

The impoverished state has poured money and resources into science and technology that has enabled it to put a satellite into orbit and conduct its third nuclear test.

“The newest addition to the North Korean asymmetric arsenal is a growing cyber-warfare capability,” said James Thurman, commander of the US forces in South Korea.

“North Korea employs sophisticated computer hackers trained to launch cyber-infiltration and cyber-attacks” against South Korea and the US, he said.

A 2010 report from South Korea’s National Intelligence Service put the number of professional hackers in North Korea’s cyber-warfare unit at 1,000.

Kim Heung-kwang, a North Korean defector, said thousands of students were recruited to North Korea’s top science schools and he trained them to become future hackers.

Cyberspace is becoming an “ideal” battleground for North Korea:

“North Korea has nothing to lose in a cyber battle,” Kim Seeongjoo, a professor at Seoul-based Korea University’s Department of Cyber Defense, told AP. “Even if North Korea turns out to be the attacker behind the broadcasters’ hacking, there is no target for South Korean retaliation.”