Facebook, WhatsApp, Messenger and Instagram are back up and running after more than seven hours of global outage.
The sites have been down for several hours across the world with social media users experiencing connection issues.
Platforms were forced to use competitor site Twitter to announce the outage after reports before 5pm this evening.
Security experts speculated the problem came following network changes, with the cause still unconfirmed by late Monday evening.
Adam Leon Smith, of BCS, The Chartered Institute for IT and a software testing expert, said: “The outage is caused by changes made to the Facebook network infrastructure.
“Many of the recent high-profile outages have been caused by similar network level events.
Get the latest headlines sent straight to your inbox with our newsletter
Did you know you can keep up to date with the latest news by signing up to our daily newsletter?
We send a morning and lunchtime newsletter covering the latest headlines every day.
We also send coronavirus updates at 5pm on weekdays, and a round up of the week’s must-read stories on Sunday afternoons.
Signing up is simple, easy and free.
You can pop your email address into the sign up box above, hit Subscribe and we’ll do the rest.
Alternatively, you can sign up and check out the rest of our newsletters here.
“It is reported by unidentified Facebook sources on Reddit that the network changes have also prevented engineers from remotely connecting to resolve the issues, delaying resolution.
“Notably, many organisations now define their physical infrastructure as code, but most do not apply the same level of testing rigour when they change that code, as they would when changing their core business logic.”
However, cyber security specialist Jake Moore said there is a “chance” the issue could be related to a cyber attack.
He told the PA news agency: “There have been many reports and I’m struggling to find out exactly what has happened- I’m reading it could be DNS related, which means there is an issue with the connection not knowing where to go to your device.
“It could well be a human error or a software bug lurking in the shadows but whatever it is Facebook needs to do its best to mitigate the problem of causing more panic about this.
“The biggest problem is fears over a cyber attack but as we saw from Fastly in the summer I would hedge my bets on that not being the case as we’re talking about one of the biggest companies in the world, but there’s always a chance.”
The New York Times reported the issue likely stemmed from a misconfiguration of Facebook’s server computers, which were not letting people connect to its sites like Instagram and WhatsApp.
It said the problems appeared to be more complex and required some manual updating.
Mike Schroepfer, Facebook’s chief technology officer, said on Twitter: “*Sincere* apologies to everyone impacted by outages of Facebook powered services right now.
“We are experiencing networking issues and teams are working as fast as possible to debug and restore as fast as possible.”
Data on the web service monitoring platform DownDetector showed that almost 50,000 people had reported the outages on Facebook by just after 5pm.
Most complaints cited issues with the website (72%), while others were linked to issues with the server connection and the app.
More than 75,000 had complained about WhatsApp, with 43% reporting issues with the app itself, while 28% cited the server connection and 28% relating to sending messages.
More than 30,000 Instagram users also had similar complaints, with 51% relating to the app, 26% over the server connection and 23% citing the website.
A graph on the DownDetector website showed a clear spike from after 4pm.
Facebook’s share price plummeted 4.9% amid the outage, which also came the day after a whistleblower claimed in a US interview that the company prioritises its own interests over the public good.
The platforms were affected by outages in 2019- in an incident which saw £FacebookDown, £instagramdown and £whatsappdown trending worldwide on Twitter.
A few months prior, users of Facebook and Instagram reported being unable to open pages or sections on the apps.
Whatsapp said in a statement: “We’re aware that some people are experiencing issues with WhatsApp at the moment.
“We’re working to get things back to normal and will send an update here as soon as possible. Thanks for your patience.”
Instagram said: “Instagram and friends are having a little bit of a hard time right now, and you may be having issues using them. Bear with us, we’re on it.”
A Facebook company spokesperson said: “We’re aware that some people are having trouble accessing our apps and products.
“We’re working to get things back to normal as quickly as possible, and we apologise for any inconvenience.”
The issue also affected other platforms such as Twitter amid an increase in traffic on its website and app.
Twitter Support tweeted: “Sometimes more people than usual use Twitter. We prepare for these moments, but today things didn’t go exactly as planned.
“Some of you may have had an issue seeing replies and DMs as a result. This has been fixed. Sorry about that!”
It had earlier joked: “”Hello literally everyone.”
Please check back regularly for updates on this developing story HERE. Get email updates on
the day’s biggest stories straight to your inbox by signing up for our newsletters.