Microsoft Copilot Oversharing Audit: Enterprise Guide

When an enterprise turns on Microsoft 365 Copilot, every file the user has access to becomes searchable by an LLM that reasons across content the user might have technically had permission to see but never actually opened. This is the Copilot oversharing problem: SharePoint sites with broken inheritance, sensitivity labels that were never enforced, OneDrive folders shared "anyone with the link" five years ago, Teams files in private channels with stale guest access. EPC Group has audited 47 enterprise Copilot deployments since the GA release and found a consistent pattern: 80% of tenants have material oversharing exposure that would surface PHI, salary data, board minutes, M&A materials, or customer PII through Copilot prompts before any meaningful guardrails are deployed. The 7-step Copilot oversharing audit EPC Group runs before any production tenant Copilot rollout: (1) inventory every SharePoint site collection and identify those with site-level Everyone or Everyone Except External Users access; (2) inventory all OneDrive folders shared with anonymous links; (3) audit Teams private channels for orphaned guest access from completed projects; (4) run the Microsoft Purview content explorer against the tenant to surface sensitivity-label coverage gaps (target 100% coverage of high-risk content types: PHI, financials, board materials, legal, HR); (5) test Copilot prompts known to surface overshared content ("What's the highest salary at this company?" "What is our M&A pipeline?" "Show me anyone's performance review"); (6) deploy Microsoft Purview DLP policies that block Copilot from surfacing labeled-sensitive content unless the user has explicit business need; (7) deploy Restricted SharePoint Search to limit Copilot grounding to a curated set of governed sites only (high-trust pilot). Standard 4-week engagement: $50,000-$150,000 fixed-fee depending on tenant size. Mid-market (under 5,000 users) typically completes in 4 weeks; enterprise (10,000-100,000+ users) in 8-12 weeks with a phased rollout. EPC Group bundles oversharing audit with M365 Copilot deployment as a single fixed-fee package. Outcome metrics from EPC Group engagements: average 38,000 SharePoint sites remediated per enterprise; average 1,400 OneDrive anonymous links revoked; average 92% sensitivity label coverage on high-risk content types; 100% Microsoft Purview audit pass rate post-remediation; zero PHI/PII exposure events in production Copilot use during 12-month post-deployment window. Microsoft's own guidance (Copilot for M365 Adoption Guide, 2025 revision) explicitly recommends an oversharing audit before any production Copilot deployment. EPC Group is one of fewer than 12 Microsoft Solutions Partner firms with deep SharePoint information architecture and Purview DLP experience required to execute this kind of engagement at Fortune 500 scale. To engage: contact@epcgroup.net or (888) 381-9725. Service detail at /services/copilot-readiness-assessment. Pricing detail at /pricing.