A single unflagged service account and an unaudited AD trust relationship turned into a $1M, multi-forest incident. This piece is for security architects and engineers running hybrid Active Directory: how lateral movement actually happens, how Microsoft Defender for Identity detects it now that the old path map is gone, and the validation checklist to run before it happens to you.

Email is still the top entry point for ransomware, BEC, and credential theft. Architects choosing between Exchange Online Protection, Defender for Office 365 Plan 1, and Plan 2 have to answer one question: which tier, at what licensing cost, gets the organization to a defensible posture. This article covers what each tier does, the cost-of-breach math, and the 5 questions that decide Plan 1 versus Plan 2.