The state-run operator of South Korea's nuclear power plants has separated its internal computer network from the Internet in an effort to guard against possible North Korean cyber attacks, Yonhap News Agency reported Sunday.
It said Korea Hydro & Nuclear Power Co. has also completely divided its nuclear plant control systems from its internal computer networks and restricted both systems' access to the Internet, while USB ports of the plant control systems have also been sealed.
The network separation is the safest way of protecting the nuclear power plants from hacking attacks from the outside, the company explained to Yonhap.
South Korea has 23 reactors nationwide, which generate around 35 percent of the country's electricity.
Last week, South Korea's government said North Korea was behind the massive hacking attack that paralyzed the networks of local financial firms and broadcasters on March 20.
Three South Korean banks — Shinhan, NongHyup and Jeju — and their insurance affiliates as well as three TV broadcasters — KBS, MBC and YTN — were hit by the cyber attack as malicious code infected some 48,000 computers in their network.
Yonhap said North Korea is known to operate a cyberwarfare unit of 3,000 elite hackers who are trained to break into computer networks to steal information and distribute malware.
In addition to the hacking attacks, it said, the North has been interfering with global positioning system signals since 2010, disrupting hundreds of South Korean commercial ships and flights in the border area.