Microsoft Security Division

Rule Changes

Leading enterprise-wide security transformation

On January 12, 2026, millions of Teams users woke up to find their security settings had changed overnight. Microsoft activated weaponizable file blocking, malicious URL detection, and phishing protections across every organization still using default configurations—no administrator approval required. Days earlier, it had expanded Zero-Hour Auto Purge malware removal to all Defender for Office 365 Plan 1 customers. These moves are part of Microsoft's $34 billion bet on 'secure by default' security, following Russian and Chinese attacks on its networks in 2023.

Updated May 20