Local user and group permissions for Excel are valid on any computer

If you specify permissions on ranges in a Microsoft Excel workbook to allow users access to parts of that protected workbook, a user without permissions may be able to edit those ranges on a different computer.

This behavior can occur if all of the following conditions are true:

• A local user or group on your computer is given permission to edit the range.
• A local user or group with the same name exists on another computer.
• A user on another computer, who either has that local user name or who is a member of that local group, opens the workbook.

To work around this issue, give permissions to domain users and groups instead of local users and groups.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Microsoft Windows NT, Microsoft Windows 2000, and Windows Vista have access control lists (ACLs) that contain computer, user, and group names. When you open a workbook in which the permission to edit ranges is assigned to a user or group, Windows NT, Windows 2000, and Windows Vista match the user name or group name with a valid member in the ACL. If a local user or group matches the text, that local user or group has permission to edit the range.