Microsoft blames faulty network upgrade for multi-day 365 outage
Microsoft said it found no evidence of malicious activity and has resolved the root cause, as Outlook and other services began recovering.
Microsoft said the multi-day outage that hit Microsoft 365, Outlook and Teams was caused by a faulty network upgrade, and that it has found no evidence of malicious activity, according to TechCrunch. The company said it has resolved the root cause and is continuing to restore the remaining services.
Microsoft said the problem arose during a previously performed network capacity upgrade and surfaced after a recent network change. The company ruled out AI as the cause of the disruption.
By the morning of November 13 US Eastern time, Outlook had begun recovering and some email services were being restored, Microsoft said.
Kentik's Doug Madory said traffic was returning to Microsoft services after about an 18-hour disruption.
A second day of disruption
The outage began on November 12, initially affecting services in the US and the Americas before spreading worldwide. It started with Outlook email and Teams video meetings and spread to other services, blocking access to Microsoft 365, Outlook, Teams and OneDrive.
James Perriman, a professor of computer science at the University of Reading in the UK, called it one of the longest and most damaging outages in Microsoft 365's history, noting that a problem that usually clears in hours had lasted into a second day. The Financial Times said the outage again showed the world economy's heavy dependence on a few core technology companies.
Quick answers
What caused the Microsoft 365 outage?
Microsoft said the cause was a faulty network upgrade, not AI, and that it found no evidence of malicious activity.
Which services were affected?
Microsoft 365, Outlook, Teams and OneDrive were affected, with access blocked during the disruption.
Are Microsoft services working again?
Microsoft said it had resolved the root cause and was restoring remaining services. By the morning of November 13 US Eastern time, Outlook had begun recovering and some email services were being restored.