Facebook reveals more details about how Christchurch terror attack video spread

Facebook has revealed more details about the spread of the Christchurch terror attack video, and its seemingly relentless attempts to stop it.

The social media giant said in a post the video was watched fewer than 200 times during the live broadcast, and that it was watched around 4,000 times in total before being removed.

Facebook said it received a user report 29 minutes after the original video started, and 12 minutes after the live stream had finished.

The company also revealed it removed the attacker's video "within minutes" of being contacted by the New Zealand Police. Before Facebook was alerted, a link to a copy of the video hosted on a file-sharing site was already posted on 8chan.

The original video was hashed to remove existing and further posts. Digital hashing breaks down a video and stores it on a database, so that it can be employed to prevent visually similar videos from appearing.

Facebook said other variations of the video, like screen recordings, were harder to detect, and so it employed audio technology to weed them out.

Within 24 hours of the attack, Facebook said it removed 1.5 million instances of the video, with 1.2 million of those videos blocked at upload. It's since shared 800 visually-distinct videos of the attack to a collective database.

Despite their efforts, Facebook and other social media platforms have come under intense scrutiny due to the continued spread of the video.

Internet service providers in New Zealand and Australia have taken action against sites which host the video, although curiously, this enforcement so far doesn't seem to apply to social media platforms.

On Tuesday, New Zealand Prime Minister Jacinda Ardern said she had "some communication" with Facebook's chief operating officer Sheryl Sandberg on the issue.

"We have been in contact with Facebook; they have given us updates on their efforts to have it removed, but as I say, it’s our view that it cannot — should not — be distributed, available, able to be viewed," she said, as per the Associated Press.

"It is horrendous and while they’ve given us those assurances, ultimately the responsibility does sit with them."