Microsoft has added stronger security and governance controls for Microsoft 365 Copilot, but the biggest risk is still your own Microsoft 365 data estate. Copilot does not create new permissions. It works with the files, chats, emails and SharePoint content a user is already allowed to access, as Microsoft explains in its guidance on how Copilot works inside your existing permissions.
That is why the first job before a wider rollout is not the AI model. It is your access control. Check who can already see what across SharePoint, Teams and OneDrive. Confirm whether confidential files are labelled and encrypted. Then make sure Microsoft Purview controls, auditing and data loss prevention are configured before Copilot reaches a wider group of users.
Why the risk changes with Copilot
Copilot can make old permission problems visible very quickly. A salary spreadsheet sitting in a Teams site shared with “Everyone except external users” may have gone unnoticed for years. Before Copilot, someone had to know where to look. After Copilot, a simple prompt could surface the same information to anyone who already had access to that overshared site.
That is not a Copilot bypass. It is a permissions problem exposed by a faster search and summarisation tool. Microsoft’s own data protection guidance says Copilot can only summarise or reference content the user is authorised to access, and that sensitivity labels, encryption, SharePoint controls and Purview policies all affect what Copilot can use.
The controls have improved. Microsoft Purview now provides specific controls for Microsoft 365 Copilot and Copilot Chat, including Purview data loss prevention for Copilot. These can restrict web grounding when prompts contain sensitive information types, block certain labelled files and emails from being processed, and support monitoring through DLP alerts and auditing. Some features are generally available, while others remain in preview, so check your tenant before relying on a control.
What to review before you widen access
| Review area | What to check | Where it usually lives |
|---|---|---|
| Permissions | Remove broad access such as “Everyone except external users” from sensitive SharePoint sites | SharePoint admin centre, Entra ID |
| Oversharing | Identify stale links, guest access and old project sites | SharePoint Advanced Management, DSPM for AI |
| Labelling | Apply sensitivity labels and encryption to confidential content | Microsoft Purview |
| DLP | Restrict sensitive prompts, labelled content and external web grounding where supported | Purview DLP for Copilot |
| Access | Require MFA, compliant devices and sensible session controls | Conditional Access, Intune |
| Auditing | Confirm prompts, responses and referenced content are logged and retained appropriately | Purview Audit |
| Connectors and agents | Limit agents and Graph connectors to the data they genuinely need | Copilot Studio, Microsoft Graph connectors |
Permissions come first because they are the slowest part. In a large tenant, cleaning up years of broad sharing can take weeks. Start before launch, not after users have already found sensitive files through prompts.
If you cannot remediate every site in time, Microsoft’s Restricted SharePoint Search can be used as a temporary measure. It lets administrators control which SharePoint sites appear in organisation-wide search and Copilot experiences, but it is not a security boundary and is not meant as a long-term fix.
Regular vulnerability management services and routine vulnerability scanning can help surface the misconfigurations, stale permissions and unmanaged exposure that make Copilot rollout riskier than it needs to be.
Monitor the rollout, not just the setup
Turn on auditing and actually review it. Microsoft says Copilot interaction data can be captured for prompts, responses and referenced content through Purview audit and compliance tools. That evidence matters if sensitive information appears somewhere it should not.
A managed SOC service can help spot unusual Microsoft 365 access patterns, while MDR services give you people who can respond if an account is misused or data exposure is suspected. A short security assessment before rollout is usually cheaper than investigating a data leak afterwards.
Roll out in phases. Start with IT, security and a small business pilot. Review what Copilot can see, fix surprises, then expand. Treat connectors and agents with the same caution, because each new data source widens what Copilot can reach on a user’s behalf.
Frequently asked questions
Does Microsoft 365 Copilot use my company data to train its AI?
Microsoft states that Microsoft 365 Copilot does not use your files, prompts, responses or Microsoft Graph data to train foundation models, and that Copilot operates within the Microsoft 365 service boundary.
Can Copilot see files I am not allowed to open?
No. Copilot works with content the user already has permission to access. The real risk is overshared content that the user should not have been able to access in the first place.
What should I fix first before rolling out Copilot?
Start with permissions. Remove broad access from sensitive SharePoint and Teams sites, apply sensitivity labels to confidential files, and configure DLP and audit controls before you scale the licence rollout.
Staff also need to know what not to paste into prompts and how Copilot uses company data. Short, regular cyber security awareness training helps turn the policy into everyday behaviour.
If you want a second pair of hands to review permissions, labelling, DLP and monitoring before you scale Copilot, Northern Star’s managed IT support services in London can help you get the groundwork right. Call the team on 0800 319 6032 to talk it through.
Focus on Active Threat Defense and Infrastructure Management
Securing a modern enterprise demands continuous vigilance across every device, server, and cloud network. The engineering experts at Northern Star design tailored environments using London Microsoft Azure services and integrated London Microsoft 365 solutions. We also implement Microsoft Copilot consulting for AI efficiency, while reinforcing safety protocols with customized cybersecurity training and robust email security in London.
Beyond user safety, we secure your perimeter by resolving weaknesses using vulnerability management in London. Our 24/7 managed security operations center works alongside proactive managed detection and response in London to intercept threats. Should an outage occur, our cyber incident response services and structured business continuity planning guarantee rapid recovery. Get in touch with us today.
