Incident response is the control family that is half configuration and half paperwork, and the paperwork is the part assessors push on. NIST 800-171 wants an operational capability, and DFARS 7012 adds a hard 72-hour clock for reporting a cyber incident.
Route security alerts to your responders (3.6.1)
NIST 800-171 3.6.1 requires an operational incident-handling capability, which starts with alerts actually reaching a human. In the Defender portal, configure alert notifications to your security distribution list, and assign owners and severities so nothing sits unworked.
Document your IR plan and the 72-hour path (3.6.1 to 3.6.3, DFARS 7012)
NIST 800-171 3.6.1 to 3.6.3 and DFARS 7012 require an incident-response plan and reporting a cyber incident to DIBNet within 72 hours. Write the plan: roles, severities, containment and escalation. Document the DIBNet 72-hour reporting path so nobody is figuring it out during an actual incident, and run at least one tabletop exercise so the plan has been tested once before you need it.
A note on what "done" means
Configuring these settings hardens your Microsoft 365 GCC High tenant to the NIST 800-171 technical baseline. It is not a CMMC certification. A C3PAO assesses your documented System Security Plan, not your tenant directly, so the configuration above only counts once it is written down with evidence. Our free GCC High Setup Autopilot walks you through every step in order and hands the result to your control set when you move to Readyline Pro.
