NEW YORK: Facebook and Instagram appeared to be partially reconnected to the global Internet on Monday afternoon (Oct 4), nearly six hours into an outage that paralysed the social media platform.
Facebook and its WhatsApp and Instagram apps went dark at around noon (Tuesday, 12am, Singapore time), in what website monitoring group Downdetector said was the largest such failure it had ever seen, with 10.6 million problem reports globally.
Around 5.45pm, some Facebook users began to regain partial access to the three apps.
In a blog post late on Monday, Facebook said the outage was caused by a "faulty configuration change", without specifying who executed the change and whether it was planned.
The outage was the second blow to the social media giant in as many days after a whistleblower on Sunday accused the company of repeatedly prioritising profit over clamping down on hate speech and misinformation.
"To every small and large business, family, and individual who depends on us, I'm sorry," Facebook Chief Technology Officer Mike Schroepfer tweeted, adding that it "may take some time to get to 100 per cent".
Shares of Facebook, which has nearly 2 billion daily active users, fell 4.9 per cent on Monday, amid a broader selloff in technology stocks.
Security experts said the disruption could be the result of an internal mistake, though sabotage by an insider would be theoretically possible.
"Facebook basically locked its keys in its car," tweeted Jonathan Zittrain, director of Harvard's Berkman Klein Center for Internet & Society.
"Facebook and related properties disappeared from the Internet in a flurry of BGP updates," tweeted John Graham-Cumming, the chief technology officer at Cloudflare.
Users trying to access Facebook in affected areas were greeted with the message: "Something went wrong. We're working on it and we'll get it fixed as soon as we can."
Soon after the outage started, Facebook acknowledged users were having trouble accessing its apps but did not provide any specifics about the nature of the problem or say how many users were affected by the outage.
The error message on Facebook's webpage suggested an error in the Domain Name System (DNS), which allows web addresses to take users to their destinations. A similar outage at cloud company Akamai Technologies Inc took down multiple websites in July.
Facebook's engineering team apologised as the apps started to come back online.
"To the huge community of people and businesses around the world who depend on us: we're sorry," the team tweeted on Monday.
"We’ve been working hard to restore access to our apps and services and are happy to report they are coming back online now. Thank you for bearing with us."
"Apologies to everyone who hasn’t been able to use WhatsApp today," tweeted the messaging app. "We’re starting to slowly and carefully get WhatsApp working again.
"Thank you so much for your patience."
Several Facebook employees who declined to be named said that they believed that the outage was caused by an internal routing mistake to an Internet domain that was compounded by the failures of internal communication tools and other resources that depend on that same domain in order to work.
The social media giant, which is the second largest digital advertising platform in the world, was losing about US$545,000 in US ad revenue per hour during the outage, according to estimates from ad measurement firm Standard Media Index.
On Sunday, Frances Haugen, who worked as a product manager on the civic misinformation team at Facebook, revealed that she was the whistleblower who provided documents underpinning a Wall Street Journal investigation and a Senate hearing on Instagram's harm to teen girls.
Haugen was due to urge the US Congress on Tuesday to regulate the company, which she plans to liken to tobacco companies that for decades denied that smoking damaged health, according to prepared testimony seen by Reuters.