Image copyright Sony Pictures Image caption Sony film The Interview has featured highly in hackers' demands

A month after hackers launched an attack on Sony Pictures, the fallout initially led the Hollywood studio to cancel the release of satirical comedy The Interview, which involves a plot to assassinate North Korean leader Kim Jong-un.

The entertainment company later allowed a theatrical and online release of the movie at Christmas, which took $15m (£9.6m) and was downloaded more than two million times in its first few days.

The initial hack, which exposed embarrassing emails and personal details about some of the world's biggest movie stars, escalated after the supposed hackers made threats against cinemas showing the film.

It has turned into one of the most difficult and damaging episodes in recent Hollywood history. Here, we examine the complicated catalogue of events.

How did it start?

On November 22, there were signs that Sony's computer system had been compromised when skulls appeared on employees' screens with a message threatening to expose "secrets" from data obtained in a sophisticated hack.

This initially caused crippling computer problems for workers at Sony, who were forced to work with pen and paper. "We even fired up our fax machine," one employee told the LA Times.

Sony initially said they were dealing with an "IT matter", but later acknowledged the hack to staff, calling it a "brazen attack" comprised of "malicious criminal acts".

Who is responsible?

Media playback is unsupported on your device Media caption North Korean TV denied involvement in the cyber attack

A unknown group calling itself #GOP - later identified as Guardians of Peace - claimed it was behind the cyber attack, prompting the FBI to launch an investigation. Their name has been attached to subsequent leaks of information.

Speculation has since mounted that North Korea may have had a hand in the attack as a form of retaliation for Sony's release of The Interview.

A North Korean foreign ministry spokesman called the movie an "act of terrorism" in June, promising "merciless" retaliation if it was released.

The country eventually denied involvement, but heaped praise on the hack, calling it a "righteous deed". The secretive nation's ability to wage cyber warfare is not unknown, but it has not previously used the name Guardians of Peace.

News network Bloomberg has reported that the perpetrators worked from a hotel in Thailand, while unnamed Sony executives told TMZ the hackers were helped by insiders who knew where the most embarrassing information could be found. US media quoted anonymous officials as saying that the FBI had linked North Korea to the attacks.

Why was the release of The Interview pulled?

Image copyright AFP Image caption Hackers have warned cinemas against screening The Interview

The fallout from the hack escalated after the "Guardians of Peace" claimed they would attack cinemas showing the Sony film. They alluded to 9/11 in their message and said it was a response to the "greed of Sony Pictures".

The film's New York premiere was cancelled and cinema chains cancelled screenings, leading Sony to announce that it had "decided not to move forward with the planned December 25 theatrical release".

However the decision has been greeted with incredulity by some in Hollywood.

"Wow. Everyone caved," actor Rob Lowe wrote on Twitter. "The hackers won. An utter and complete victory for them. Wow."

Comedian Jimmy Kimmel tweeted that the decision by theatres to refuse to show the film was "an un-American act of cowardice that validates terrorist actions and sets a terrifying precedent."

On 23 December, Sony announced that the film would have a limited theatrical release and be made available for download.

What did the hackers steal?

Image copyright AP Image caption Annie - starring Cameron Diaz - has been leaked as a result of the hack

Before the controversy around The Interview, reams of data considered confidential by Sony - and some of the company's prime assets - were stolen in the hack.

An early version of a script for the next James Bond movie, Spectre, was leaked but failed to halt production.

Five Sony films, including the new and unreleased version of Annie, turned up on illegal file-sharing sites and were downloaded up to a million times. Brad Pitt's Fury, which had already hit cinema screens, was also shared.

What information has been revealed?

A whole host of Sony's private company information has apparently been exposed to the public, including bosses' salaries and employees' social security information.

Strings of confidential emails between Sony workers have also been circulated and proved to be the most sensitive and embarrassing leaks.

The emails revealed that:

Female film stars including Amy Adams and Jennifer Lawrence were paid less than their male co-stars.

Sony executive Amy Pascal made jokes about black-themed movies that might be among President Obama's favourites.

Angelina Jolie was branded a "minimally talented spoiled brat" in a private email from producer Scott Rudin.

George Clooney lost sleep over bad reviews for The Monuments Men and emailed Pascal to say: "I've let you all down. Not my intention. I apologize. I've just lost touch… Who knew?"

Sony has contacted some media outlets asking them to exercise caution over the leaked material they report on.

How did Hollywood respond?

Image copyright Getty Images Image caption Oscar winner Aaron Sorkin has railed against the fall-out of the hack

A-listers at the heart of the revelations have maintained a dignified silence.

But screenwriter and producer Aaron Sorkin wrote in the New York Times of his anger at the hack, accusing the media of aiding and abetting the cyber criminals by sifting through the leaked information and reporting the most salacious findings. He hit out at Hollywood for doing little to protect the dignity of Sony employees, whose personal data has been stolen.

James Franco and Seth Rogen, stars of The Interview, have also commented publicly on the hack, using colourful language on US "shock jock" Howard Stern's show to refer to the "stolen information", adding that its circulation is "doing exactly what these criminals want".

When Sony relented and released the film, Rogen, who also wrote and directed The Interview, said: "I'm so grateful that the movie found its way into theatres, and I'm thrilled that people actually went out and saw it."