Check what Copilot can reach before you switch it on

Microsoft 365 Copilot is useful because it can draw on your organisation’s documents, chats and email. It does so with the permissions of the person asking, so it does not get special access and it does not get round anything.

The less comfortable part is that most tenants (a tenant being your organisation’s own space in Microsoft 365) hold years of permissions that nobody has looked at. Copilot does not create over-sharing, but it does make existing over-sharing very easy to find. Before rollout, a file that was technically open to everyone was usually safe enough, because nobody knew it was there. After rollout, anyone can ask a plain question and receive an answer drawn from it.

Where the exposure usually sits

• Sites shared with “Everyone except external users”. Old project sites, intranet pages and team sites often use this group, and it includes every internal account.
• “Anyone with the link” and “People in your organisation” links. These take seconds to create and often never expire, so a salary spreadsheet shared once with one manager can stay reachable for years.
• Teams files. Every Team has a SharePoint site behind it, and files posted in a channel inherit that site’s permissions, including any broad groups added along the way.
• Inherited permissions. A folder shared widely passes that access down to everything saved in it afterwards.
• Guests. External people added to a Team for one project have a habit of staying long after it has finished.

What you can do before rollout

1. Find the over-shared sites first. Start with sites that use “Everyone” or “Everyone except external users”, and sites with many sharing links. If you have SharePoint Advanced Management, its data access governance reports are built for exactly this job. Look first at sites holding HR, finance, legal or customer data.

2. Review sharing links and broad groups. Remove organisation-wide links where nobody needs them, set an expiry on “anyone” links, and check that broad security groups on sensitive sites are still meant to be there. It is also worth changing the default link type in the SharePoint admin centre, so that new links are limited to specific people unless someone chooses otherwise.

3. Apply sensitivity labels and data loss prevention. Microsoft Purview lets you label content (Confidential or Highly Confidential, for example) and attach protection to those labels. Data loss prevention policies can then stop labelled or sensitive content being shared in ways it should not be. Labels take a while to roll out properly, so start with the content that matters most rather than trying to label everything at once.

4. Check identity and access in Entra ID. Make sure conditional access (the rules that decide who can sign in, from where and on what device) covers the people who will use Copilot. That usually means multi-factor authentication, compliant or managed devices where that makes sense, and sensible rules for sign-ins from unfamiliar places. Review guest accounts and remove any that nobody can explain. Access reviews can turn this into a regular habit rather than a one-off tidy-up.

5. Agree a usage policy. Write down, in plain language, what staff can and cannot use Copilot for, what to do with its output (it can be wrong, and it sounds just as sure of itself when it is), and whom to ask when they are not sure. A single page is plenty to start with.

6. Pilot with a small group. Choose people from a few departments, including at least one person who works with sensitive data day to day, and ask them to tell you about anything Copilot shows them that they did not expect to see. Every surprise is a permission to fix before the wider rollout.

7. Keep an eye out for shadow AI. If the approved tool is slow to arrive or awkward to use, people will paste their work into consumer chat tools instead, and that data leaves your tenant entirely. Find out what people are already using, give them an approved route, and make sure the policy covers both.

None of this is a reason to wait

We would not suggest putting Copilot off indefinitely. Most of these steps are good housekeeping you would want done anyway, and the most important ones (broad groups and links on sensitive sites) are usually the quickest to fix. The aim is to switch Copilot on knowing what it can reach, rather than finding out from a user.

How we can help

We run AI Readiness assessments for Microsoft 365. One of our team works through your permissions and sharing, identity and conditional access in Entra, sensitivity labels and data loss prevention, licensing and shadow AI with your IT lead. At the end, we leave you with a remediation plan in priority order and a usage policy your staff can actually follow. If you have questions before then, we are happy to answer them.