Social media giant, Facebook, has revealed the cause of its longest-ever outage which occurred on Monday night.

WuzupNigeria reported that millions of Facebook users as well as those of its sister companies Instagram and WhatsApp were unable to access the apps from 4:30pm local time.

The global outage lasted for about six hours forcing Facebook’s share price to drop by 4.9% amid the outage, according to UK Metro.

WuzupNigeria also reported that the outage cost the tech giant $7billion and the stock slide on Monday sent owner, Mark Zuckerberg’s worth down to $120.9 billion, dropping him below Bill Gates to No. 5 on the Bloomberg Billionaires Index.

However, Facebook tendered an apology via a Twitter statement 11.31pm, thanking “the huge community of people and businesses around the world…for bearing with us.”

Revealing the cause of the of the outage which lasted for about six hours, Facebook management said in a statement that the outage was caused by a “faulty configuration change”

The statement said, “Our engineering teams have learned that configuration changes on the backbone routers that coordinate network traffic between our data centres caused issues that interrupted this communication.

“This disruption to network traffic had a cascading effect on the way our data centres communicate, bringing our services to a halt.

“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.”