The head of the FBI has said he is confident North Korea was behind the November cyber attack 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 cyber security 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 revealed 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.