Copilot is coming to Microsoft 365: should you tidy up your sharing before switching it on?

The scenario in brief

A made-up example, for illustration. A fictional 25-person SME switches on Microsoft 365 Copilot to save time on meeting notes and emails. In the second week, a salesperson asks Copilot: “What are our salary bands?” Copilot answers, figures included, and cites its source: an Excel salary file stored in the “Management” folder.

Nobody hacked anything. In 2022, that folder had been shared with a link valid for “everyone in the organisation”, so that an intern could help prepare the payroll. The link was never removed. Before Copilot, you had to search for that exact file or know the folder to stumble on it. With Copilot, all it takes is the right question.

Copilot really does save time, but within seconds it exposes the over-broad sharing built up over the years. The right time to tidy it up is before you switch it on.

Copilot doesn’t hack anything: it finds what was already open

Microsoft 365 Copilot (which Microsoft is gradually renaming “Microsoft Copilot”) is an AI assistant built into Outlook, Teams, Word, Excel and your company’s file spaces (SharePoint and OneDrive). It answers questions by searching your emails, your meetings and your documents.

Microsoft states it plainly: Copilot only shows organisational data that a user has at least permission to view. It grants no new access. In other words, it opens no doors: it switches on the light in every room whose door was already open, including the ones you had forgotten about. An old, forgotten share that bothered nobody now surfaces at the first question asked in everyday language, with a link to the document.

Basic version or paid licence: what Copilot can read

Not everyone gets the same Copilot. According to Microsoft’s documentation, the basic version, included in eligible Microsoft 365 subscriptions, mainly answers from the internet and from the documents you give it. The paid licence, on the other hand, searches across all your Microsoft 365 data.

In every case, Microsoft states that Copilot respects existing permissions. Tidying up your sharing is therefore useful today, and it becomes essential the day you buy paid licences.

The doors left open almost everywhere

In its Copilot readiness guide, Microsoft asks you to start by identifying sites that are overshared, ownerless, inactive or that hold sensitive data. In practice, in an SME or a practice, the same situations come up almost every time:

• “Anyone with the link” links: anyone who has received the link can open the document without signing in. Microsoft points out that you then cannot tell who has access.
• “People in your organization” links: if the link is forwarded, it works for any colleague. Handy for a team document, risky for salaries or patient records.
• The “Everyone except external users” group: added to a site or folder, it gives access to every account in the company. Microsoft recommends removing it from sensitive sites.
• Ownerless or abandoned sites: an old project, a former partner, a folder from 2018. Nobody keeps an eye on them, but Copilot reads them for everyone who has access.
• Folder-by-folder exceptions: a folder whose permissions were changed by hand no longer follows the rules of the site it sits in. Microsoft calls this “broken inheritance” of permissions: that is often where the surprises hide.

External guests count too: an accountant, a former supplier or a lab once added as a guest keeps their access until someone removes it. Microsoft even points out that if you turn external sharing off and then back on, guests get their access back.

Healthcare practice: a record seen by the wrong person is a data breach

For a medical, dental or physiotherapy practice, the stakes go beyond internal embarrassment. The GDPR, as the European Data Protection Board explains, defines a personal data breach as a security incident that leads, accidentally or unlawfully, to the unauthorised disclosure of, or access to, personal data, among other things.

• What counts as a breach: access by someone who should not have seen the document, even without malicious intent. For example, a consultation report that a receptionist comes across through Copilot.
• The deadline: notify the Data Protection Authority without undue delay, where feasible within 72 hours.
• The exception: no notification if the breach is unlikely to present any risk to patients.

In its brochure on AI and the GDPR, the Belgian Data Protection Authority also lists, for health data, strict access controls that limit who can access and modify patient data. That is exactly what to check before switching Copilot on.

The four-week plan before you switch it on

There is no need to block everything or audit everything at once. Here is a realistic sequence for an organisation of 5 to 50 people. Your IT provider handles the technical side; management decides who should see what.

The default link setting matters a lot: Microsoft describes the “Specific people” option as the most restrictive. “Anyone” links can also be limited to view-only and forced to expire after a chosen number of days, according to the sharing settings described by Microsoft.

If Copilot is already switched on

Don’t panic, and there is no need to turn everything off. Microsoft’s guide provides temporary safeguards: you temporarily hide sensitive sites from Copilot’s searches while you fix their permissions, then lift that protection. According to Microsoft, some of these tools (advanced SharePoint management) are included with the Copilot licence; others depend on your Microsoft 365 subscription. After that, you apply the same plan as above.

What you can do on Monday morning

1. Write down the five folders that nobody but you should see: salaries, contracts, disputes, accounting, patient records.
2. Open each of them in SharePoint or OneDrive, click “Manage access” and look at who is listed. An “Everyone” entry or a link open to the whole organisation should be removed.
3. Ask your IT provider for the list of “Anyone with the link” links still active and the list of external guests.
4. Name an owner for each shared space: they will confirm, twice a year, whether the access is still right.
5. Plan a pilot: two or three people test Copilot with questions such as “show me the salaries” or “which patients have appointments tomorrow?”, to check what comes up.

The ground rules for the team

The technical clean-up is not enough: the team needs to know what is expected of them. Since 2 February 2025, the EU AI Act has required companies that use an AI system to take measures so that their staff understand how it works and its risks. The European Commission makes clear that no certificate is required: a short internal training session, with a record kept, shows that the step has been taken.

Three simple messages to get across:

• Copilot sees what you see. If an answer shows a document you should not see, don’t pass it on: report it to management or the IT provider, it is a door to close.
• Copilot can get things wrong. Microsoft points out that its answers are not guaranteed to be 100% accurate: read before you send.
• We share with people, not with “everyone”. For a sensitive document, the right reflex is the “Specific people” link.

On confidentiality, Microsoft states that questions, answers and the data accessed are not used to train its AI models. So the real question is not “does Microsoft read our data?” but “can our colleagues read data that has nothing to do with them?”.

Well prepared, Copilot saves time on emails, meeting notes and document searches. A few weeks of tidying up are enough to enjoy it without nasty surprises.

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