Is Copilot safe for confidential information?

Copilot answers from the emails, chats and files the person asking already has permission to open. Microsoft says Copilot "only surfaces organizational data to which individual users have at least view permissions."

A file you cannot open never shows up in your answers. A file you can open can, even one you never knew existed.

SourceData, Privacy, and Security for Microsoft Copilot

No. Microsoft says "Prompts, responses, and data accessed through Microsoft Graph aren't used to train foundation LLMs, including those used by Microsoft Copilot." Microsoft Graph is how Copilot reaches your emails, chats and files. Microsoft also says "Your customer data stays within the Microsoft 365 service boundary."

So the question is which of your own staff can open what.

SourcesData, Privacy, and Security for Microsoft CopilotHow does Microsoft Copilot work?

Yes, if the person asking can open them. Copilot draws on an index Microsoft builds from all your company's text based SharePoint files, not just the ones people have opened. Microsoft calls it "an organization-wide index generated from text-based SharePoint Online files" and says it only shows a result to a person who "already has access to the content".

So a file nobody has touched in three years is still within reach of everyone who can open its site.

SourceSemantic indexing for Microsoft Copilot

Nobody has to do anything wrong. A team sets up a public site so colleagues can join it, and Microsoft adds everyone at the company to the site's Members group by default. Microsoft's own guide to one of its site templates offers "Everyone except external users" as a way to share the site "with everyone in your organization". Each made sense on the day.

Before Copilot, someone had to know the file existed and go looking for it. Now they can ask a question.

SourcesEveryone except external users group is removed on Microsoft 365Add the Workplace transformation site

Only some of them. A sensitivity label marks how confidential a file is, and some labels also protect it. If a label's encryption lets someone view a file but not copy from it, Microsoft says "Copilot won't summarize this content but can reference it with a link." That person can still open the file from the link.

A label that does not encrypt the file does not change who can open it. On its own it changes nothing for Copilot, unless your IT team also sets a data loss prevention rule for it.

SourceConsiderations for Microsoft Purview to manage Microsoft 365 Copilot

Microsoft's own Copilot setup guide asks administrators to "identify, assess, and mitigate oversharing risks". Its steps include switching off Everyone except external users, the group that means every staff member, across your whole Microsoft 365. It also says to turn on Purview Audit, which keeps a record of Copilot activity.

Microsoft's privacy page gives the reason. "It's important that you're using the permission models available in Microsoft 365 services, such as SharePoint, to help ensure the right users or groups have the right access to the right content within your organization."

SourcesSet Up Microsoft Copilot and Assign LicensesData, Privacy, and Security for Microsoft Copilot

1. Step 01

   In the document library, select the file.

2. Step 02

   Select Share above the list of files. If the file is shared, a row of circles appears at the bottom left of the Share window.

3. Step 03

   Select the circles to open the Manage Access panel. Microsoft says it shows "the People who have access, the Groups who have access, and the Links used to give access to the file."

If you see Everyone except external users, the Members group of a site anyone at the company can join, or a link anyone can open, more people can open the file than a confidential file needs. Doing that for every file on every site is the slow part.

SourceSee who a file is shared with in OneDrive or SharePoint

Yes, when you are signed in with your work account. Microsoft says your prompts and Copilot's answers are not used to train the AI, and are stored in line with the commitments that cover the rest of your Microsoft 365 content. What Copilot shows back is limited to what the person asking can open.

Copilot signed in with a personal Microsoft account is different. It has its own privacy page, which says it does not cover work accounts.

SourcesData, Privacy, and Security for Microsoft CopilotMicrosoft Copilot for individuals: your data, privacy, and responsible AI

Yes, every file the person asking can open, and none they cannot. Microsoft says "Copilot doesn't access data that the user doesn't have permission to access."

SourceHow does Microsoft Copilot work?

Your data stays inside Microsoft 365 and does not train the AI. Microsoft says "Microsoft Copilot presents only data that each individual can access." So it comes down to who can open it. If a confidential file sits on a site the whole company can open, fix who can open it before you switch Copilot on.

SourcesHow does Microsoft Copilot work?Data, Privacy, and Security for Microsoft Copilot