Microsoft Outage Not a Cyber Attack, Company Says, as Fixes Roll Out
Microsoft said a global outage that knocked out Outlook, Teams and Copilot for nearly 24 hours was a technical fault, not a security breach. Problems were reported in at least 74 countries, and the company warned some users may still see delays as email catches up.
Microsoft said the global outage that disrupted Outlook, Teams and its Copilot AI assistant for almost 24 hours was not a cyber-security incident but a technical fault. So, is there a cyber attack going on right now? Not in this case, according to the company, which has apologized for the disruption.
Problems with Microsoft 365 were reported in at least 74 countries, hitting schools, healthcare systems, businesses, courts and governments.
Reports of Outlook problems peaked globally at nearly 140,000 around 18:00 GMT on Thursday, according to the monitoring site Downdetector.
From late Thursday, many customers could not send or receive emails or view certain files and calendar details. Some users could still use Teams, messaging and online meetings.
Microsoft first said the outage was caused by a number of servers "being unexpectedly unavailable", which strained its remaining systems. It later attributed the problem to an issue during an earlier network capacity upgrade.
"We have addressed the underlying issue and continue to restore service to remaining customers and regions," the company said on Friday.
By Friday afternoon, Microsoft reported "encouraging recovery progress" in Europe and improvement in North America. It said email queues were "significantly reduced and approaching normal levels". It also warned that "some users may still experience intermittent issues".
Delayed messages remain a risk. Microsoft extended the email "timeout window" to 48 hours, meaning Outlook will wait longer to receive mail. Late arrivals will carry the time they were delivered, not the time they were sent.
The outage also hit AI companies that work with Microsoft's systems, including Anthropic and OpenAI. OpenAI said it was investigating an issue affecting its connections to Microsoft's services, which left some tools not working as expected.
Electric truck maker Workhorse Group moved its third-quarter results from November 12 to November 16. It cited business disruptions caused by the Microsoft outage.
Users in the US, Japan and Singapore were among those affected. Microsoft had also reported an outage of its Azure cloud platform last month.
Why the fix took so long
Prof James Ferryman of the University of Reading's department of computer science said the details Microsoft disclosed offer clues. "What Microsoft has told us is that the part of its servers that sets up secure connections is getting swamped, and once that happens the server just stops answering," he said.
He said such failures snowball. "You can't just turn it all back on at once. You have to bring it back bit by bit."
Gergely Orosz, a former software engineer at companies including Skype and Uber, said this could be the "most disruptive" business email outage "of all time". He said he "cannot recall" a business email outage taking this long to return to normal.
Australian cyber-security expert Troy Hunt said the outage could have far-reaching consequences. "Microsoft is a massive part of the internet backbone and reminds us how critical email still is," he said.
