How to block Microsoft 365 Copilot: three methods, and what each one really blocks

First: there are two Copilots

• Microsoft 365 Copilot: the managed enterprise service that works with your organization's data. Everything in this post applies to it.
• Microsoft Copilot with a personal Microsoft account: the consumer experience. It runs in the same Microsoft Copilot app as the work experience, and data doesn't flow between the two.

Block only the enterprise service and employees can still sign in to Microsoft Copilot with a personal Microsoft account, and maybe paste company data into it. Microsoft's guidance is not to block copilot.cloud.microsoft to stop personal accounts. Use tenant restrictions v2 to control personal Microsoft account sign-in instead. Services like ChatGPT and Gemini are different: you block those on the endpoint, for example with Defender for Endpoint. More on AI tools your organization doesn't manage in AI meeting notetakers taking over your organization.

Before you block: Teams depends on SharePoint and OneDrive

Files in Teams channels live in SharePoint. Files shared in chats live in the sender's OneDrive. So any SharePoint or OneDrive block also hits parts of Teams. Tell users and management before you start. How SharePoint and Teams fit together, and what to fix before you open Copilot, is in SharePoint and Teams security before Microsoft 365 Copilot.

Method 1: a full block with Conditional Access

• How: a Conditional Access policy that blocks Microsoft 365 Copilot, and SharePoint Online and OneDrive if needed, for the relevant user group.
• What users see: a generic "access blocked" message.
• Licence: Entra ID P1, included in Microsoft 365 Business Premium, E3 and E5. Business Basic and Standard don't include Conditional Access.
• Upside: simple, predictable, and it works on every device and app.

Method 2: blocking through Defender for Cloud Apps

• How: mark the app as unsanctioned (the block itself works on devices with Defender for Endpoint network protection, or through a supported proxy), or route access to it through session control.
• What users see: a clearer message you can customize.
• Licence: requires Defender for Cloud Apps, plus Defender for Endpoint for the block itself.

Method 3: blocking uploads and downloads only

• How: a Defender for Cloud Apps session policy that blocks file uploads and downloads and leaves the app open for everything else.
• The limit we found: the block only applies to files from outside, meaning from the device or external storage. Attaching a document from inside the organization's apps still works.

What we learned in the field

We also tried blocking only specific components, and got the opposite of what we wanted:

• Teams was blocked completely.
• OneDrive kept working partly.
• Even apps that weren't blocked started throwing errors.

It blocked where it shouldn't and didn't block enough where it should.

Our advice: start with a full Conditional Access block, then open up step by step, app by app and group by group. And always test in a lab first.

Comparison

After the block: open up with control

Blocking is only the first step. When you're ready to open Copilot, do it with controls: access, oversharing cleanup, DLP and monitoring. We cover this in 5 practical steps to secure Microsoft 365 Copilot, and we run the whole process, from block to rollout, in our Copilot security service.

Sources

• Microsoft Learn: Zero Trust for Microsoft Copilot
• Microsoft Learn: Microsoft Copilot app
• Microsoft Learn: govern discovered apps
• Microsoft Learn: Secure Microsoft Copilot for small businesses
• Microsoft Learn: proxy intro aad
• Microsoft Learn: sharepoint onedrive interact
• Microsoft Learn: indicator ip domain