Federal Agency Deploys SharePoint in GCC High — FedRAMP High Authorization

Project Overview

A US federal agency with defense-adjacent missions needed to migrate its SharePoint environment to Microsoft 365 Government Community Cloud High (GCC High) to meet CMMC 2.0 Level 2 requirements and handle Controlled Unclassified Information (CUI) at scale.

The Challenge

Federal compliance requirements created unique constraints:

- FedRAMP High requirements: All systems must meet FedRAMP High baseline — 421 security controls across 17 control families

• CUI handling: Over 2 million documents contained Controlled Unclassified Information requiring NIST 800-171 controls
• Personnel security: Migration team required security clearances for access to CUI during migration
• Authority to Operate (ATO): Any new system must have ATO before going live — process typically takes 6-18 months
• Legacy customizations: 200+ SharePoint Designer workflows, 40+ InfoPath forms, 15 custom web parts
• No cloud before: Agency had never deployed cloud services — extensive internal resistance from IT security team

  Our Solution

  Phase 1: ATO Pathway (Months 1-4)

  Microsoft 365 GCC High carries FedRAMP High Provisional Authorization to Operate (P-ATO) from FedRAMP PMO. This gave us a path to accelerated ATO:

• Leveraged Microsoft's P-ATO to demonstrate federal security baseline
• Documented agency-specific controls needed beyond the P-ATO
• Engaged agency's Authorizing Official (AO) early to align on control inheritance model
• Completed System Security Plan (SSP) documenting 421 controls

  Phase 2: CUI Information Protection Configuration

  Before migrating a single document, we configured the information protection infrastructure:

  *Sensitivity Labels for CUI:*

``` CUI Category Labels: ├── CUI (General) — NIST 800-171 controls ├── CUI//PRVCY — Privacy Act data, additional restrictions ├── CUI//SP-CTI — Cyber Threat Intelligence └── CUI//SP-EXPT — Export-controlled technical data (EAR/ITAR) ```

*Auto-labeling policies detected CUI indicators:*

• DoD classification markings in document headers
• Export control numbers (ECCN, USML categories)
• Privacy Act system identifiers
• ITAR-controlled technical specifications

  Result: 2.1 million documents automatically labeled over 45-day crawl period.

  Phase 3: Phased Migration

  Migration executed in phases by classification sensitivity:

1. Unclassified non-CUI documents first (50% of volume) 2. CUI General documents (clearance-required migration team) 3. CUI with specialized categories (subset of cleared team with need-to-know)

Phase 4: Legacy System Modernization

200+ SharePoint Designer workflows converted to Power Automate:

• Simple notification workflows (73 flows) rebuilt in 1 day each using Power Automate templates
• Document approval workflows (91 flows) rebuilt in 2-4 days each
• Complex procurement workflows (36 flows) required custom Power Automate + Power Apps solutions
• 15 custom web parts rebuilt as modern SPFx components

  40 InfoPath forms replaced with Power Apps (36) and SharePoint JSON forms (4).

  Results

  FedRAMP authorization maintained with zero gaps:

Agency received its Authorization to Operate for GCC High before cutover date. First federal cloud ATO completed by this agency in its history.

CUI compliance transformed: Pre-migration: Manual document review required to identify CUI — estimated 4 FTE dedicated to CUI marking compliance. Post-migration: Automated labeling handles initial classification; human review focused on exceptions only. CUI marking compliance improved from estimated 60% to measured 98%.

Operational efficiency:

• Compliance reporting time reduced 60% through automated evidence collection from Microsoft Purview
• Audit preparation time reduced from 6 weeks to 2 weeks (evidence pre-collected in Purview Compliance Manager)
• Legacy system maintenance costs eliminated ($2.4M annually)

  Workforce adoption:

• 95% of users accessing GCC High via compliant devices within 30 days
• Zero CUI data spills in first 12 months post-migration (previous 12 months: 7 spills)