Facebook has finally given a reason for the six-hour outage Monday

Facebook posted Monday night in a blog that the six hour outage that brought it offline, along with Instagram Messenger, Whatsapp and OculusVR, was caused by a configuration change to its routers. This was not a hack attempt or attempt to access user data. Although the explanation is not detailed, it appears like Facebook's machines couldn't talk to each other. Facebook claims that the disruption in network traffic caused a cascading effect to the way our data centers communicate, which brought our services to an abrupt halt.
Mark Zuckerberg, CEO, posted Monday evening an apology saying that the platforms would be back online. Sorry for today's disruption. I understand how important it is to be connected with those you love.

The company experienced widespread problems Monday morning after the outage started at 11:40 AM ET. This was the worst Facebook outage since 2019, when it was down for over 24 hours. The site was down for more than 24 hours, preventing employees from communicating with one another on company message boards. Some told The Verge that they used work-provided Outlook email addresses to communicate.

Problems began with a routine BGP upgrade that went wrong. This wiped out DNS routing information required by Facebook to allow other networks to locate its sites.

The Facebook outage occurred just a day before Frances Haugen, a whistleblower about her experiences at the company, was scheduled to testify before Congress. Haugen, who was a former Facebook product manager and worked in its Civic Integrity group provided a wealth of documents from within Facebook to Wall Street Journal reporters. On Sunday, she told 60 Minutes that Facebook is responsible for our safety and pays for its profits.