its servers had become "unexpectedly unavailable".
Microsoft has been hit by a huge outage, taking down Outlook and Teams and causing chaos across the world.
The issues began on the afternoon of November 12 and have continued into the following day.
Because so many organisations rely on Microsoft’s tools, it has already caused problems everywhere from hospitals to airports.
According to Microsoft, the problems were affecting its 365 Services, which include messaging app Teams, email service Outlook and and its Copilot AI tool.
More than 430 million people use those services, according to Microsoft’s website, including many of the world’s biggest companies and most important organisations.
Amid the disruption, many speculated that the problems could be the result of a cyber attack. That gained particular prominence because of widespread fears that the growing power of artificial intelligence tools could bring disruptive outages of this kind.
But experts and Microsoft itself both say that there is no evidence that the technical issues are actually the result of a cyber attack.
Instead, it seems to be a more innocent if equally concerning mistake.
Microsoft said the outage came because of “elevated load”, not because of an increased amount of traffic but because its servers had become “unexpectedly unavailable”.
It has not said exactly why those servers became unavailable.
Previous similar problems have been caused by everything from physical incidents such as fires at data centres to errant updates that take the systems online, which appears most likely in this case.
The company said it had no evidence of “malicious activity” and executive vice president Charles Lamanna said Microsoft had ruled out a cyber attack.
Experts agreed that it appeared to be the result of a “bug”, though the exact details of it remain unclear.
Despite the fact that there was no evidence of a hack, security experts warned that it could nonetheless be used by cyber criminals to launch attacks of their own.
Aiden Sinnott, principal threat researcher at Sophos Counter Threat Unit, said:
“Although the Microsoft outage is not a cybersecurity issue, bad actors will be looking to take advantage of concerned individuals, offering a resolution or assurances.
“At this time, even more so than usual, people should exercise caution when receiving emails, texts or calls purporting to be from Microsoft or other affected businesses, particularly banks or shops.
“Be aware of requests for urgent action, sharing of personal information and avoid clicking on links sent via message or email.”
Professor Junaid Arshad, Head of the Department of Computer Science at Birmingham City University said the outage “highlights the profound risks embedded within our critical infrastructure’s reliance on centralised cloud ecosystems”.
He added: “Although early reports from Microsoft indicate issues with server availability and configuration challenges rather than a malicious cyberattack, the cascading real-world impact on government and public services, education, and enterprise operations is immense.
“This incident is a stark reminder that resilience requires more than just high availability; organisations must adopt robust redundancy, proactive contingency planning, and robust local failover mechanisms.
“When core cloud services become unavailable, supply chains and public services can stall.
“This incident also reminds us about the importance of digital sovereignty and the need to prioritise operational continuity to withstand centralised infrastructure failures.”
