A building with offices belonging to Microsoft is seen in Maryland, on January 18, 2023. (AFP)

In early June, sporadic but serious service disruptions troubled Microsoft’s flagship office suite — including the Outlook email and OneDrive file-sharing apps — and cloud computing platform.

Microsoft was initially reluctant to identify the cause but has now confirmed that DDoS attacks by an obscure upstart were in fact to blame.

"Beginning in early June 2023, Microsoft identified surges in traffic against some services that temporarily impacted availability," the company said in a blog post.

The software giant, however, has provided little data and declined to comment on the severity of the attacks. Additionally, it would not provide information on the number of clients that were impacted or the attackers.

On June 5, the Microsoft 365 software suite—which includes Teams and Outlook—was unavailable for more than two hours to over a thousand customers, with a brief repeat the next morning. For Microsoft, it was the fourth such disruption in a year.