'The Interview' Packs U.S. Theaters On Christmas Day

North Korea has called the film an "act of war." But to the millions of moviegoers who watched "The Interview" in more than 300 movie theaters all over the United States on Christmas Day, it was just a funny movie.

The Sony Pictures comedy film starring Seth Rogen and James Franco about a fictional plot to assassinate North Korean leader Kim Jong Un filled up U.S. theaters with some of the fans saying they're championing freedom of expression.

Sony finally released the $44-million movie for public viewing after initially cancelling its release. The film company backtracked after U.S. President Obama, lawmakers from both sides of the fence, and Hollywood luminaries including George Clooney raised concerns that Hollywood was setting a precedent of self-censorship.

Sony's initial action was in part based on a decision by major U.S. theater chains to pull out the film because of threats of violence by a group of hackers who call themselves Guardians of Peace. The group also claimed that they were the ones responsible for the devastating cyberattacks on Sony last month. The United States has blamed the attacks on the North Korean regime.

On Thursday, movie theater managers and patrons alike said they were not worried about the threats and no security issue was reported in the initial screening.

The movie features Rogen and Franco as journalists who are recruited by the CIA to assassinate the North Korean leader.

The film has also been made available to U.S. online viewers through Google Inc's Google Play and YouTube Movie, as well as on a Sony website, www.seetheinterview.com. 

Meanwhile, doubts were raised on U.S. government claims that North Korea was responsible for the hacking of Sony's computer systems.

A number of private security researchers noted that Washington based its findings on evidence that it refuses to release, citing the "need to protect sensitive sources and methods."

The researchers say this is not good enough. "Essentially, we are being left in a position where we are expected to just take agency promises at face value," said Marc Rogers, a security researcher at CloudFlare, a mobile security company.

Rogers and other Internet security experts said they have been studying the evidence presented by the U.S. government on Pyongyang's complicity in the cyberattacks. The experts said the evidence publicly mentioned was hardly conclusive.

The experts noted that the malware samples from the hacked Sony computers showed that the hackers routed their attack through computers all over the world. They said one of those computers was in Bolivia and was used by the same group to hack targets in South Korea.

But that particular computer and others in Poland, Italy, Thailand, Singapore, Cyprus and the United States that were similarly used were all freely available to anyone to use, the experts said. As such anyone with an Internet connection and basic hacking skills could have done the cyberattacks, they argued.

The security experts also pointed out that whoever attacked Sony had a deep knowledge of its computer systems. This was because the names of company servers and passwords were all hard-coded into the malware, suggesting that the hackers were inside Sony before they launched their attack.

The experts said it's possible the cyberattacks were an inside job.

Rogers said the attack appeared to have been made by an angry "insider." He noted that days before attack, Sony had announced plans to lay off a number of its workers. "You don't have to stretch the imagination too far to consider that a disgruntled Sony employee might be at the heart of it all," Rogers said.