The Korea Hydro & Nuclear Power Co was hit by a hack earlier this month and data stolen from its system.
But the South Korea energy ministry said today that the control systems for three nuclear reactors were unaffected by the hack, according to a Reuters report.
The energy minister told the South Korean parliament that the worm was most likely transmitted to the computer systems by an infected USB device – a claim that some have their doubts about.
The CEO of Korea Hydro and Nuclear Power told the parliament that all of the country’s reactors were invulnerable to viruses and worms. But nevertheless he said that the firm was hiring more IT security staff to be on the safe side.
Some people believe that North Korea is behind attacks on South Korea computer installations. The two countries are still technically at war with each other.