The unprecedented hack of Sony Pictures which a U.S. official says is linked to North Korea may be the most damaging cyberattack ever inflicted on an American business, AP reported. The fallout from the hack that exposed a trove of sensitive documents, and this week escalated to threats of terrorism, forced Sony to cancel release of the North Korean spoof movie 'The Interview.' The studio's reputation is in tatters as embarrassing revelations spill from tens of thousands of leaked emails and other company materials. Federal investigators believe there is a connection between the Sony hack and the isolated communist nation, according to an official who spoke on condition of anonymity. The official was not authorized to openly discuss an ongoing criminal case. North Korea has denounced the 'The Interview' but earlier this month said the hack might have been carried out by sympathizers. The movie features a pair of journalists played by James Franco and Seth Rogen who are asked by the CIA to assassinate North Korea's leader Kim Jong Un. The attack is possibly the costliest ever for a U.S. company, said Avivah Litan, a cybersecurity analyst at research firm Gartner. 'This attack went to the heart and core of Sony's business and succeeded,' she said. 'We haven't seen any attack like this in the annals of U.S. breach history.'