CMMC Microsoft 365 Defense Contractor Deployment — 2026 Guide

Cybersecurity Maturity Model Certification (CMMC) became mandatory for the Defense Industrial Base in 2025-2026 phased rollout. Defense contractors handling Controlled Unclassified Information (CUI) must achieve CMMC Level 2 (110 NIST 800-171 controls); contractors handling more sensitive CUI need Level 3 (134 controls). For Microsoft-stack contractors, this almost always means migrating from M365 Commercial to GCC High — a major operational change with material licensing, integration, and user-experience implications. EPC Group has executed CMMC-driven GCC High migrations for 9 defense contractors and aerospace primes. The 14-control framework: (1) license posture — M365 GCC High E5 minimum for CMMC Level 2 contractors handling CUI; (2) tenant separation — GCC High tenant separated from any commercial tenant, with cross-tenant authentication where required; (3) Microsoft Entra ID Government for identity; (4) Conditional Access policies tuned for CMMC requirements; (5) Microsoft Purview for CUI classification with required dissemination markings; (6) DLP policies that block CUI transmission to unauthorized destinations; (7) Microsoft Defender for Office 365 with CMMC-tuned phishing thresholds; (8) Microsoft Defender for Endpoint Plan 2; (9) Microsoft Sentinel feeding to contractor-side SIEM with 6-year retention; (10) Customer Lockbox enabled for all support scenarios; (11) Audit (Premium) for 6-year audit log retention; (12) Microsoft Intune for endpoint management; (13) Azure Government Cloud for any compute or storage workloads; (14) audit-ready evidence pack with NIST 800-171 control crosswalk, SSP, POA&M, and 3PAO assessment support. Engagement: CMMC GCC High Migration ($350,000-$950,000 fixed-fee, 14-22 weeks) — full migration from commercial to GCC High, NIST 800-171 control implementation, 3PAO C3PAO assessment support, post-migration continuous monitoring runbook; CMMC Readiness Assessment ($95,000 fixed-fee, 6 weeks) — gap analysis vs Level 2 or Level 3 baseline, ATO timeline forecast, board-ready briefing. EPC Group has supported 9 defense contractor CMMC Level 2 authorizations and 2 Level 3. Outcomes: average 16-week time-to-CMMC-Level-2 reduction versus DIY, 100% C3PAO assessment pass rate, zero post-certification continuous monitoring findings in 12-month observation. Errin O'Connor's FedRAMP framework heritage gives EPC Group rare combined NIST 800-171 + 800-53 fluency. To engage: contact@epcgroup.net or (888) 381-9725. Detail at /cmmc-compliance-consulting and /services/microsoft-365-consulting.