The head of the FBI has said he is confident North Korea was behind the November cyberattack on Sony Pictures Entertainment.

James Comey said on Wednesday that threats made against the Japanese company were traced to Internet Protocol addresses used exclusively by the North Koreans.

Comey made the remarks at a cybersecurity conference at New York's Fordham University.

He said there was evidence that North Korea had sought to use proxy servers to conceal the Sony hack, but he added that sometimes the hackers "got sloppy" and did not use the servers.

Earlier on Wednesday, US Director of National Intelligence James Clapper r
evealed that he had previously dined with the North Korean general believed responsible for the hack.

He said the meeting took place two months ago during his secret mission to Pyongyang. 

Clapper said on November 7, the first night of his mission to free two Americans, he dined with General Kim, " [who was] in charge of the Reconnaissance General Bureau, the RGB, the organisation responsible for overseeing the attack against Sony".

He did not give the general's full name but he apparently was referring to General Kim Yong-chol, director of the RGB, also known as Unit 586, one of three North Korean entities sanctioned by the US in response to the hack.

'Vitriol' over dinner

Clapper called the elaborate, 12-course repast "one of the best Korean meals I've ever had," but said the four-star general spent most of the time berating him about US aggression "and what terrible people we were".

"All the vitriol that he spewed in my direction over dinner was real," Clapper said. 

"They really do believe they are under siege from all directions and painting us as an enemy that is about to invade their country every day is one of the chief propaganda elements that's held North Korea together."

He said the pair communicated through a North Korean translator who spoke fluent English "with a British accent, which was kind of strange".

The FBI first announced that it had evidence that North Korea was responsible for the hack last month. 

North Korea denied responsibility and called for a joint investigation with the US, warning of "serious consequences" if Washington did not co-operate. 

The US has retaliated, with President Barack Obama signing an executive order allowing sanctions against three North Korean organisations and 10 individuals.

Source: Agencies