Facebook and its Instagram and WhatsApp platforms were down in parts of the world today. Facebook's internal systems used by employees also went down. Service has not yet been restored.
The company did not say what might be causing the outage, which began around 11:45am ET Monday (4.45am NZT today). Websites and apps often suffer outages of varying size and duration, but hours-long global disruptions are rare.
It is now understood that many locked out Facebook users in New Zealand have been able to get back on the site.
"This is epic," said Doug Madory, director of internet analysis for Kentik Inc. The last major internet outage, which knocked many of the world's top websites offline in June, lasted less than an hour. The stricken content delivery company in that case, Fastly, blamed it on a software but triggered by a customer who changed a setting.
Facebook's only public comment so far was a tweet in which it acknowledged that "some people are having trouble accessing (the) Facebook app" and that it was working on restoring access. Regarding the internal failures, Instagram head Adam Mosseri tweeted that it feels like a "snow day."
Two Facebook security team members, who spoke to the New York Times on condition of anonymity because they were not authorised to speak publicly, said it was unlikely that a cyberattack caused the issues. That's because the technology behind the apps was still different enough that one hack was not likely to affect all of them at once.
The Wall Street Journal reported the problems appeared to be linked to a change that Facebook made to networking instructions for how the world accesses its systems, according to outside experts.
So many people are reliant on Facebook, WhatsApp or Instagram as a primary mode of communication that losing access for so long can make them vulnerable to criminals taking advantage of the outage, said Rachel Tobac, a hacker and CEO of SocialProof Security.
"They don't know how to contact the people in their lives without it," she said. "They're more susceptible to social engineering because they're so desperate to communicate." Tobac said during previous outages, some people have received emails promising to restore their social media account by clicking on a malicious link that can expose their personal data.
The cause of the outage remains unclear. Malory said it appears that Facebook withdrew "authoritative DNS routes" that let the rest of the internet communicate with its properties.
Such routes are part of the internet's Domain Name System, a key structure that determines where internet traffic needs to go. DNS translates an address like "facebook.com" to an IP address like 188.8.131.520. If Facebook's DNS records disappeared, apps and web addresses would be unable to locate it.
Jake Williams, chief technical officer of the cybersecurity firm BreachQuest, said that while foul play cannot be completely ruled out, chances were good that the outage is "an operational issue" caused by human error.
Madory said there was no sign that anyone but Facebook was responsible and discounted the possibility that another major internet player, such as a telecom company, might have inadvertently rewritten major routing tables that affect Facebook. "No one else announced these routes," said Madory.
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.
Meanwhile, on Twitter, users congratulated themselves for their choice of app.
Twitter also chimed in from the company's main Twitter account, posting "hello literally everyone" as jokes and memes about the Facebook outage flooded the platform. Later, as an unverified screenshot suggesting that the facebook.com address was for sale circulated, Twitter CEO Jack Dorsey tweeted, "how much?"
The outages come a week after major outages shut down workplace messaging tool Slack and Kiwi accounting software Xero.
Mobile communications worldwide have also been hit by an outage today after US companies AT & T, Verizon and T-Mobile all suffered problems, locking out millions of users.
Facebook is going through a major crisis after the whistleblower who was the source of The Wall Street Journal's series of stories exposing the company's awareness of internal research into the negative effects of its products and decisions went public on 60 Minutes in the US on Sunday.
Frances Haugen was identified in a 60 Minutes interview as the woman who anonymously filed complaints with federal law enforcement that the company's own research shows how it magnifies hate and misinformation, leads to increased polarisation and that Instagram, specifically, can harm teenage girls' mental health.
The Journal's stories, called The Facebook Files, painted a picture of a company focused on growth and its own interests instead of the public good. Facebook has tried to play down the research. Nick Clegg, the company's vice president of policy and public affairs, wrote to Facebook employees in a memo on Friday that "social media has had a big impact on society in recent years, and Facebook is often a place where much of this debate plays out."
- Associated Press, additional reporting NZ Herald