Exploitation is the most common way an intrusion starts, and the median hand-off to a second threat group was 22 seconds in 2025. This guide gives CISOs and the architects who advise them a funding order for Microsoft Defender XDR: identity coverage, then automated response, then AI in the SOC. It covers where Microsoft 365 E7 fits, 8 quick wins that use licenses you may already hold, and a business case built on your own numbers.