Earlier this month, Microsoft’s Teams and Outlook were unavailable to multiple users for hours. After an investigation, Microsoft revealed the root cause to be a cyber-attack.

On Friday, Microsoft announced that the previous outages that had occurred earlier in the month were caused by cyber-attacks. The company reported that it was due to these attacks that certain services that it offered were affected. However, Microsoft also mentioned that there has been no further evidence to show any customer data being compromised or accessed in any way.

In a blog post, the company stated that starting in early June this year, the company noticed a heightened level of traffic for some of the services it provided, making them temporarily unavailable.

The company made it clear that they had opened an investigation and started to track the distributed denial-of-service (DDoS) attack by a threat, which, once identified, they referred to as Storm-1359.

When Reuters reached out to Microsoft for a response on whether or not the company had found the identity or root of the attack, it failed to do so immediately.

DDoS attacks operate by sending large amounts of internet traffic in an uncomplicated attempt to take down target servers.

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