A faulty configuration change has been blamed for taking Facebook, WhatsApp and Instagram offline for more than six hours on Monday night.
The social network's engineering team said that the changes affected the routers that coordinate the platform's network traffic between its data centres. This, they said, caused a "cascading effect" on the way its data centres communicate, bringing all of the company's services to a halt.
"Our services are now back online and we're actively working to fully return them to regular operations," the company said in a blog post. "We want to make clear at this time we believe the root cause of this outage was a faulty configuration change. We also have no evidence that user data was compromised as a result of this downtime."
In order to remedy the issue, Facebook sent engineers to one of its main data centres in California, according to The New York Times, suggesting it couldn't be fixed remotely. It was also reported that the outage prevented staff from accessing company buildings and conference rooms with their badges.
The incident caught the attention of internet giant Cloudflare, which initially assumed something was wrong with its own DNS servers. However, after an investigation, engineers realised something more serious was happening, and reported in a blog that "social media quickly burst into flames."
"Facebook and its affiliated services WhatsApp and Instagram were, in fact, all down," Cloudflare said. "Their DNS names stopped resolving, and their infrastructure IPs were unreachable. It was as if someone had 'pulled the cables' from their data centres all at once and disconnected them from the Internet."
The issues were down to BGP - the Border Gateway Protocol - which is a mechanism that exchanges routing information between autonomous systems on the web. The bigger versions of these make the internet work and have constantly updated lists for the possible routes of traffic, according to Cloudflare.
"The Internet is literally a network of networks, and it's bound together by BGP," the firm said in its blog. "BGP allows one network (say Facebook) to advertise its presence to other networks that form the Internet. As we write Facebook is not advertising its presence, ISPs and other networks can't find Facebook's network and so it is unavailable."
