N. Korea's Internet links restored amid U.S. hacking dispute

North Korea, at the center of a confrontation with the United States over the hacking of Sony Pictures, experienced a complete Internet outage for hours before links were restored on Tuesday, but U.S. officials said Washington was not involved.

U.S.-based Dyn, a company that monitors Internet infrastructure, said the reason for the outage was not known but could range from technological glitches to a hacking attack. Several U.S. officials close to the investigations of the attack on Sony Pictures said the U.S. government had not taken any cyber action against Pyongyang.

U.S. President Barack Obama had vowed on Friday to respond to the major cyberattack, which he blamed on North Korea, "in a place and time and manner that we choose."

Dyn said North Korea's Internet links were unstable on Monday and the country later went completely offline. Links were restored at 0146 GMT on Tuesday, and the possibilities for the outage could be attacks by individuals, a hardware failure, or even that it was done by North Korea itself, experts said.

Matthew Prince, CEO of U.S.-based Cloud Flare which protects websites from web-based attacks, said the fact that North Korea's Internet was back up ‘is pretty good evidence that the outage wasn't caused by a state-sponsored attack, otherwise it'd likely still be down for the count’.

Almost all of North Korea's Internet links and traffic pass through China and it dismissed any suggestion that it was involved as ‘irresponsible’.

Meanwhile, South Korea, which remains technically at war with the North, said it could not rule out the involvement of its isolated neighbour in a cyberattack on its nuclear power plant operator. It said only non-critical data was stolen and operations were not at risk, but had asked for U.S. help in investigating.