N. Korea Cyberwarfare Unit Hacking S. Korea, U.S. DOD, Official Says

North Korea has been operating a cyber warfare unit that seeks to hack into South Korea's military command communication network and destroy Internet servers, a South Korean intelligence official said Wednesday.

The North set up a cyber warfare unit about eight years ago with some 1,000 personnel, said the intelligence official, who declined to be named because it was the agency's policy to remain anonymous.

The North's operation, called unit 121, "has hacked into the South Korean and U.S. Defense Department" and has caused much damage in the South, the official said without elaborating.

South Korea has the world's highest per capita rate of broadband Internet connections, and cyber attacks have the potential to cripple the heavily wired society.