Initially reluctant to name the cause, Microsoft has now revealed the causes of its outages. In early June, sporadic but serious service interruptions affected Microsoft's flagship office suite — including Outlook email and OneDrive file-sharing applications — as well as the platform for managing the digital cloud

Microsoft says its outages in early June were due to attacks by a cyberactivist group that claimed responsibility, saying it had flooded sites with unwanted traffic with distributed denial of service (DDoS) attacks.

Microsoft provided few details and did not immediately indicate how many customers were affected and whether the impact was global. A spokeswoman confirmed that the group calling itself “Anonymous Sudan” was behind the attacks. He claimed responsibility on his Telegram channel at the time. Some security researchers think the group is Russian.