Microsoft outage: these failures tend to 'snowball'

Microsoft products are offline for millions of people following a global outage.

Professor James Ferryman, computer science expert, explains what is behind the global blackout.

For interviews with Professor Ferryman, contact the University of Reading Press Office on 0118 378 5757, 07867991342 or uorpressoffice@gmail.com.

Professor James Ferryman, Professor of Computer Science at the University of Reading, said:

“This is one of the longest and most disruptive outages Microsoft 365 has had. Problems like this are normally sorted in a few hours. This one has run into a second day.
The problem is in Exchange Online, which is the email and calendar system behind Outlook. Teams and Copilot rely on it too, for calendars, meetings and getting at people’s work data. So when Exchange has a bad day, a lot of other things do as well.
 
“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. The trouble is that this kind of failure snowballs. One server falls over, its work gets passed to the next one, and meanwhile huge numbers of phones and laptops keep trying to get back in. You can’t just turn it all back on at once. You have to bring it back bit by bit.
 
“We still don’t know what set it off. Microsoft says it has seen no sign of an attack so far, and we will have to wait for further details before drawing any big conclusions.

“Here in the UK you can see how much of daily life now runs through one company’s email system. Schools are asking parents to phone instead of emailing. Councils are doing the same. NHS staff in many places can’t get into their email, and patients have been warned prescriptions may be delayed. Emergency care appears to be carrying on, but a significant amount of the routine communication around it has had to go back to the telephone. Businesses of every size are in the same position.”