The users whose login were impacted in Azure or O365 had no impact on the data or applications.
User Impact: Users may have been unable to access the Office 365 service and unable to authenticate to azure active directory and dependent resources
Start time: Friday, April 6, 2018, at 8:30 AM UTC
End time: Friday, April 6, 2018, at 11:30 AM UTC
Admins affected by this issue may not have had access to the Admin center. However, updates were provided on https://status.office.com and via the twitter handle @Office365Status(https://twitter.com/Office365Status)
A subset of infrastructure that handles authentication requests became degraded, causing user sign in failures. Microsoft has recovered the affected infrastructure to mitigate impact and monitored the service to confirm resolution. A subset of infrastructure that handles authentication requests became degraded.
Also a subset of Azure Active Directory customers in East Asia and Europe may have experienced difficulties when attempting to authenticate into resources which are dependent on Azure Active Directory. Downstream impact was reported by a number of Azure services for which customers may have experienced: Backup: failures for the registration of new containers and backup/restore operations. Storsimple: new device registration failures and Storsimple management/communication failures. Azure Bot Service: bots reporting as unresponsive. Visual Studio Teams Services: higher execution times and failures while getting AAD tokens in multiple regions. Media Services: authentication failures. Azure Site Recovery: new registrations and VM replications may also have failed.
You can refer these below links to find the notifications and the Root cause for this outage.
Final Status: Azure Active Directory - Authentication Errors - Resolved
Next Steps:Microsoft is analysing the performance data and trends on the affected systems to help prevent this problem from happening again.