When revoking access to old users, or old, lost or stolen devices, it is possible that those devices retain access to key material that can be used to access old revisions of files.
While Atakama ensures all insecure/old key material is removed on current devices and cloud folders, it's possible that backups using older keys are still accessible, and that devices owned by attackers have prevented key material deletion.
By default, visitors and members of a SharePoint site (those with Read, Contribute or Edit permission level) can access the previous versions of a document or a list item. To restrict this, create a custom permission level and remove access to revisions.
Click for an article with details on how to do this for Onedrive.
In summary:
- Site Settings > Users and Permissions > Site Permissions > Permission Levels > Edit
- Copy Permission Level to create a custom Permission Level
- Scroll down and remove the "view versions" permission
- Create the new custom permission
- Assign this permission to the "Members" or other groups.
Administrators may still have access to revisions to restore or repair data.
This step can help prevent easy access to prior revisions of file that may contain copies of older or revoked credential sets.