Facebook Inc blamed a “faulty configuration change” for a nearly six-hour outage on Monday that prevented the company’s 3.5 billion users from accessing its social media and messaging services such as WhatsApp, Instagram and Messenger.
The company in a late Monday blog post here did not specify who executed the configuration change and whether it was planned.
Several Facebook employees who declined to be named had said that they believed that the outage was caused by an internal mistake in how internet traffic is routed to its systems.
The failures of internal communication tools and other resources that depend on that same network in order to work compounded the error, the employees said.
Security experts have said an inadvertent mistake or sabotage by an insider were both plausible.
The Facebook outage is the largest ever tracked by web monitoring group Downdetector.
As the world flocked to competing apps such as Twitter and TikTok, shares of Facebook fell 4.9%, their biggest daily drop since last November, amid a broader selloff in technology stocks on Monday.
Shares rose about half a percent in after-hours trade following resumption of service.
Twitter on Monday reported higher-than-normal usage, which led to some issues in people accessing posts and direct messages.
Facebook, which is the world’s largest seller of online ads after Google, was losing about $545,000 in U.S. ad revenue per hour during the outage, according to estimates from ad measurement firm Standard Media Index.
Past downtime at internet companies has had little long-term affect on their revenue growth, however.
Facebook’s services, including consumer apps such as Instagram, workplace tools it sells to businesses and internal programs, went dark noon Eastern time (1600 GMT). Access started to return around 5:45 pm ET.
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.
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.
