Baseline Security Mode (BSM) is one of the most overlooked security features in Microsoft 365. It's a single place to adopt a core set of security controls across Entra, Exchange Online, SharePoint, OneDrive, Teams and Microsoft 365 Apps.
There are things you should know before you start clicking regarding its scope and inability to reverse some changes, and how you can still achieve the BSM protections without some of these impacts as I've described here: https://davidmcwee.com/2026/10/12/baseline-security-mode-deployment/