Hackers breached Microsoft to find out what Microsoft knows about them

Microsoft disclosed that the nation-state-linked group Midnight Blizzard (also known as APT29/Cozy Bear) breached a small subset of Microsoft corporate email accounts — including senior leadership and employees in cybersecurity, legal, and related functions — by performing a password-spray attack against a legacy account. The attackers appear to have been seeking information about the group itself and what Microsoft knows about them; Microsoft did not disclose the number of accounts affected or the exact data accessed and said it will accelerate security changes to legacy systems and internal processes.