Microsoft will soon notify Office 365 of suspected nation-state hacking activity detected within tenants. Microsoft has been tracking, warning of, and disrupting state-sponsored hacking operations originating from Russia, Iran, and China for years. Alerts will be based on indicators of compromise and threat profiles collected and put together by Microsoft’s security experts. Microsoft is planning to make it generally available worldwide this month in all environments, for all Microsoft Defender for Office 365 (Office 365 Advanced Threat Protection) users. Microsoft also added priority protection for accounts of high-profile employees such as executive-level managers.
Source: https://www.bleepingcomputer.com/news/security/microsoft-to-alert-office-365-users-of-nation-state-hacking-activity/