James B. Comey, FBI head, calls North Korea a cyber threat

FBI Director James Comey says he's confident that North Korea was behind the cyberattack on Sony.

Comey said Wednesday that threats made against Sony were traced to IP addresses used exclusively by the North Koreans. He made the remarks at a cybersecurity conference at New York's Fordham University.

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Comeysaid there was evidence that North Korea had sought to use proxy servers to conceal the Sony hack. But he says they sometimes "got sloppy" and didn't use the servers.

Comeypredicted that North Korea would try to strike again.

Earlier Wednesday, Director of National Intelligence James Clapper said North Korea will continue the attacks against American interests unless the United States "pushes back."

U.S. sanctions 'an important signal'

The nation is believed to have orchestrated the attacks in retaliation for Sonys production of The Interview. The movie presents an unflattering image of North Korean leader Kim Jong-un and includes a scene of his death.

The hackers threatened violence against theatres that would screen the movie, and Sony initially decided to pull itfrom theatres.

The Interviewwas laterreleased onlineand ina limited number of theatres. Itgrossed more than $1 million USin a limited Christmas Day release.

On Monday, Sony CEOKazuo Hirai made his first public commentson the attack, praising employees and partners for standing up to the hackers' "extortionist efforts."

TheUnited States has imposed sanctions against North Korea since the attacks, targeting top state officials and defence-related organizations.

North Korea hascriticized the U.S.for the new sanctions.Comey called the sanctions "an important signal" of how seriously the government will take such attacks.