Facebook - along with Instagram, Messenger and WhatsApp - went down for more than seven hours, raising eyebrows among users as well as tech experts.
The social media giant suddenly went offline at around 4.45pm on Monday - causing a frantic operation to get the issue fixed as quick as possible.
But while that work went on behind the scenes, and witty memes were shared on Twitter, there was no explanation for the sudden outage - that also affected a number of UK phone networks too.
In the absence of any real explanation from Facebook, there were plenty of questions about the cause of the Facebook blackout and whether it was malicious or not.
The speculation that dark forces may have been at work were not surprising, given that in 2019, details of more than 530 million people were leaked in a database online, largely consisting of mobile numbers, following a hack on Facebook. Earlier this year, a leaked email from the firm suggested the social network expected more such incidents and was planning to frame it as an industry problem that was a normal occurrence.
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However, in this instance several experts believed the outage may have been caused by a technical issue instead.
The reason why this is thought to be the case is because the technology behind the apps was still different enough that one hack was not likely to affect all of them at once.
In a series of tweets, John Graham-Cumming, the chief technology officer of Cloudflare, a web infrastructure company, said the problem was likely with Facebook’s servers, which were not letting people connect to its sites like Instagram and WhatsApp.
Some have spotted that the were "major DNS failures at Facebook" prior to it going down.
DNS—short for Domain Name System—is the service which translates human-readable hostnames (like Facebook.com) to numeric IP addresses.
Cyber experts have pointed out that even though the DNS servers of Facebook seem to have vanished and are no longer connected to the internet, ones for WhatsApp and Instagram can still be reached.
However, they seem to throw other errors, indicating that internally something has gone wrong with Facebook's servers.
But one expert argued that outages "can point to a cyber attack".
Jake Moore, the former head of digital forensics at Dorset Police and now cybersecurity specialist at global cybersecurity firm, ESET told the Independent: "Outages are increasing in volume and can often point towards a cyber-attack, but this can add to the confusion early on when we are diagnosing the causes.
"As we saw with Fastly in the summer, web-blackouts are more often originate from undiscovered software bug or even human error.
"Although these are increasing in frequency and require more failsafes in place, predicting these issues is increasingly more difficult as it was never thought possible before".
Data on DownDetector's website showed that at one stage almost 50,000 people reported the outages on Facebook.
Most complaints cited issues with the website (72%), while others were linked to issues with the server connection and the app.
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