Facebook, Instagram and WhatsApp went offline for users across the globe, the social media giant said on Monday, as it worked on restoring its services. Reuters could not immediately confirm the issue affecting the services, but the error message on the webpage of Facebook Inc suggested a problem with Domain Name System (DNS). DNS allows web addresses to take users to their destinations. A similar outage at cloud company Akamai Technologies Inc took down multiple websites in July. Security experts tracking the situation said the outage could have been triggered by a configuration error, which could be the result of an internal mistake, though sabotage by an insider would be theoretically possible. An outside hack was viewed as less likely. A massive denial-of-service attack that could overwhelm one of the world's most popular sites, on the other hand, would require either coordination among powerful criminal groups or a very innovative technique. Facebook acknowledged users were having trouble accessing its apps…

Today at 1651 UTC, we opened an internal incident entitled "Facebook DNS lookup returning SERVFAIL" because we were worried that something was wrong with our DNS resolver 1.1.1.1.  But as we were about to post on our public status page we realized something else more serious was going on.