Permissions

sysadmin permissions are required for a SQL Server connection.

Permissions are not required to read .mdf or .bak files other than file read permissions.

Internals Viewer uses the DBCC PAGE command to connect to online databases. This is the only command used as everything is done from the page data. DBCC PAGE requires syadmin permissions due to the nature of the command - it can read anything in the database regardless of permissions.