Permission problems in Microsoft 365 usually stay hidden until something goes wrong. A former employee still has access to files. A manager can see data they should not. A shared mailbox has too many delegates. If you are wondering how to audit Microsoft 365 permissions, the goal is not just to clean up settings. It is to reduce business risk before it turns into downtime, data exposure, or a compliance issue.
For most small and midsize businesses, Microsoft 365 grows faster than anyone expects. New users are added, teams are created, mailboxes are shared, outside vendors need access, and nobody wants to interrupt daily work. Over time, that creates permission sprawl. An audit gives you a clear picture of who has access to what, whether that access still makes sense, and where the biggest gaps are.
Why permission audits matter
Permissions are one of the most common weak points in a cloud environment because they change constantly. Unlike a firewall rule that may stay in place for months, user access shifts with every hire, role change, leave of absence, and termination. If those changes are not reviewed regularly, your environment drifts away from least-privilege access.
That matters for security, but it also matters for operations. Too much access increases the chance of accidental deletion, misdirected email, or unauthorized sharing. Too little access creates support tickets and slows work down. A good audit helps you find the balance between protection and productivity.
How to audit Microsoft 365 permissions without missing the big risks
A useful audit starts with scope. Microsoft 365 permissions are spread across several services, so trying to review everything at once can get messy fast. Begin with the areas that usually carry the most business and security impact: admin roles, user accounts, Exchange permissions, SharePoint and OneDrive sharing, Teams membership, and guest access.
If your company is small, one careful review may be enough to establish a baseline. If your environment is larger or changes often, treat the first audit as the start of an ongoing process rather than a one-time project.
Start with privileged roles
Admin access deserves immediate attention because it gives users control over settings, identities, and data across the tenant. Review who holds roles such as Global Administrator, Exchange Administrator, SharePoint Administrator, Teams Administrator, User Administrator, and Billing Administrator.
The biggest question is simple: does each person still need that level of access today? In many businesses, the answer is no. Someone may have been given admin rights during an urgent project and never had them removed. Another user may be acting as a backup but does not need standing access all the time.
A smaller number of well-controlled admins is almost always safer than broad administrative access. At the same time, reducing access too aggressively can create support delays. It depends on your internal staffing, your support model, and whether you use emergency access accounts. The right answer is usually controlled, documented admin access rather than maximum restriction.
Review user accounts and group membership
Next, look at the basics. Confirm that every active account belongs to a current employee, approved contractor, or valid service account. Pay special attention to disabled users, shared accounts, and accounts that have not signed in recently.
Then review group memberships. In Microsoft 365, groups often drive access to mailboxes, SharePoint sites, Teams, applications, and policies. A user may not appear to have direct access, but they may still inherit it through a group that has been in place for years.
This is where many businesses find stale permissions. A user moved from accounting to operations but still belongs to a finance group. A temporary project team still grants file access long after the project ended. These issues are common because they are easy to miss in day-to-day administration.
Audit Exchange Online permissions carefully
Email is still one of the most sensitive parts of Microsoft 365. Review shared mailboxes, full access permissions, send-as rights, send-on-behalf permissions, and mailbox folder delegation.
Shared mailboxes are especially worth checking because access is often granted quickly for convenience. Over time, multiple employees may gain visibility into conversations, attachments, and sensitive client information that no longer relates to their job. That creates privacy concerns and can complicate investigations later.
Look for mailboxes with many delegates or permissions assigned to broad groups. That does not always mean the setup is wrong, but it deserves a second look. Customer service teams and executive support staff may need shared access for legitimate reasons. The goal is to confirm intent, not assume every broad permission is a mistake.
Audit SharePoint, OneDrive, and Teams access
Files are where permission sprawl tends to spread quietly. SharePoint sites, OneDrive sharing links, and Microsoft Teams channels can all expose business data more widely than intended if nobody is reviewing them.
Start with SharePoint site permissions and site owners. Too many owners can make access harder to control because more people can add members, change sharing settings, or restructure site access. Then review external sharing settings and identify files or folders shared directly with individuals instead of managed through groups.
OneDrive deserves attention because users often share files ad hoc to move work forward. That is normal, but old external links and direct shares can remain active long after the original need has passed. In a busy office, nobody remembers a file was shared with a vendor six months ago until it becomes a problem.
In Teams, review team owners, members, guest users, and private channels. Teams often feels informal, but it can hold contracts, HR conversations, customer records, and internal planning. If Teams membership is unmanaged, sensitive information can end up visible to people who should not have access.
Do not overlook guest access
Guest accounts are useful and often necessary, especially if you work with outside accountants, consultants, legal counsel, or project partners. The risk is not that guest access exists. The risk is that it stays in place forever.
Review every guest account and ask whether the relationship is still active, what resources the guest can access, and whether that access is still appropriate. If the guest is tied to a completed project, remove the account or at least remove group and team memberships that are no longer needed.
A practical policy helps here. Some businesses benefit from guest access expiration or periodic access reviews. Others need a more hands-on approach because they collaborate with outside parties regularly. Again, it depends on how your business operates.
Check sharing settings and audit logs
Permissions are only part of the picture. You also want visibility into how access is being used and how broadly sharing is allowed across the tenant.
Review tenant-level sharing settings in Microsoft 365, especially around SharePoint, OneDrive, and Teams. If external sharing is set too openly, users may be able to share content in ways leadership never intended. If it is set too tightly, staff may work around it with personal email or unmanaged file-sharing tools. The right setting supports the business without creating avoidable exposure.
Audit logs help validate what is happening in practice. They can show role assignments, file access, sharing events, mailbox changes, and other important activity. Logs are valuable during an investigation, but they are just as helpful during routine reviews because they highlight patterns you may not see from static permission reports alone.
What a good audit process looks like
The most effective permission audits are repeatable. That means documenting what you reviewed, what you changed, what still needs a business decision, and when the next review will happen.
Many companies do best with a quarterly review of high-risk access and a broader annual review of the full Microsoft 365 environment. Admin roles, guest access, and sensitive department data usually deserve more frequent attention than low-risk collaboration areas.
It also helps to assign ownership. IT can run reports and identify issues, but department leaders often need to confirm whether access is still appropriate. Finance should validate finance access. HR should validate HR access. This shared accountability produces better results than leaving every decision to one technical contact.
If your internal team is stretched thin, this is one of the areas where outside support can make a real difference. A managed IT partner like MaguroBlue can help create a clean baseline, reduce inherited risk, and put a review process in place that fits how your business actually works.
Common mistakes to avoid
The biggest mistake is treating the audit as a checkbox exercise. If you only export reports and never compare them to real job responsibilities, the problem stays in place.
Another common issue is focusing only on admins and ignoring collaboration tools. In many small businesses, the larger day-to-day risk sits in file sharing, shared mailboxes, and lingering guest access rather than in obvious administrator roles.
Finally, avoid making sweeping permission changes without checking business impact. Removing access too quickly can disrupt operations, especially in busy offices where several people may rely on shared data to keep work moving. The better approach is to prioritize high-risk access first, then clean up the rest in a controlled way.
A Microsoft 365 permission audit does not need to be complicated to be valuable. What matters is consistency, clear ownership, and a willingness to question access that has simply been there for years. When permissions match real business needs, your environment becomes easier to manage, safer to use, and less likely to surprise you at the worst possible moment.