Microsoft 365 Copilot readiness: fix oversharing before you switch it on

Microsoft 365 Copilot respects your existing permissions. It will not show a user a file they cannot open. That sounds reassuring until you remember how permissions drift over the years: sites shared with “Everyone”, links that work for anyone in the organisation, project teams that were never cleaned up.

Before Copilot, overshared files were hidden by obscurity. Nobody went looking for the salary spreadsheet in an old project site. With Copilot, a user can simply ask, and the answer will draw on anything they technically have access to.

Step 1: Measure the exposure

Start with data, not assumptions. Microsoft 365 provides reporting on sharing links, site permissions and sensitive content. You are looking for:

• Sites and libraries shared with large groups such as “Everyone except external users”.
• Organisation-wide and “anyone” sharing links on sensitive folders.
• Content that matches sensitive information types, such as SIN numbers, banking details and health information.
• Teams and sites with no active owner.

Step 2: Fix the worst first

You do not need a perfect tenant to start. Focus on the areas that would hurt most if surfaced: HR, finance, legal, executive and customer data.

• Replace broad access with named groups.
• Expire or remove organisation-wide links on sensitive libraries.
• Assign owners to orphaned sites, or archive them.
• Where a site must stay broadly accessible but should not feed Copilot answers, use the controls Microsoft provides to exclude it from organisation-wide search and Copilot discovery while you fix it.

Step 3: Label what matters

Sensitivity labels in Microsoft Purview let you classify and protect documents, and Copilot honours them: content it generates from a labelled file inherits the label’s protection. Start with a small set, such as Public, Internal, Confidential and Highly Confidential, and apply defaults at the site level so people do not have to label every file by hand.

Step 4: Pilot with the right people

Choose 20 to 50 users from different departments who will use Copilot daily and report back. Give them short, role-specific training: what to ask, what to check and how to report something they should not have seen.

Step 5: Govern the ongoing state

Permissions drift again. Put a quarterly access review on the calendar, alert on new broad-sharing links in sensitive sites, and keep an owner on every team.

The payoff

Done in this order, a Copilot rollout also delivers a cleaner, better-governed Microsoft 365 tenant, which pays off even for staff who never use AI.

Our Managed IT & Cybersecurity practice runs Copilot readiness assessments that cover exposure, labelling and pilot design in a fixed scope.