Guest access in Microsoft 365 enables B2B collaboration by allowing external users from other organizations (or personal accounts) to access your resources.
How guest access works:
1. User invites external email address
2. Invitation sent to guest
3. Guest accepts and creates Entra ID guest account
4. Guest can access shared resources
- *Guest access locations:
- Microsoft Teams (channels, chats, meetings)
- SharePoint sites and files
- OneDrive file sharing
- Microsoft 365 Groups
- Power BI dashboards
- Other apps with guest support
Security risks:
1. Stale access - Guests retained after projects end
2. Overpermissioning - More access than needed
3. Unmanaged accounts - Personal emails without corporate security
4. Data exposure - Sensitive files shared externally
5. Compliance violations - Regulated data shared inappropriately
How to secure guest access:
- Restrict who can invite:
- - Limit to admins only
- - Or specific users/groups
- - Not allow guests to invite others
- Control which domains:
- - Allow list: Only approved partners
- - Deny list: Block specific competitors/regions
- Set guest expiration:
- - Automatic removal after 90-180 days
- - Force re-invitation for continued access
- Limit permissions:
- - Restrict guest access in Teams settings
- - Configure SharePoint external sharing levels
- - Block access to sensitive content labels
- Require access reviews:
- - Regular review of all groups with guests
- - Owners must verify continued need
- - Automatic removal if not approved
TrueConfig controls EXT-01, EXT-02, and EXT-03 monitor your guest access configuration.