Tableau workbooks can be shared securely via Tableau Server. When we want to share dashboard with data and someone who is supposed to view does not have access to Tableau Server and can only view via Tableau reader, then file has to be saved with data as .twbx file format. Tableau Public can also be used where users can create dashboards and share / publish to other users. Of course these will include – user level filter criteria, database level security, application or environment level security etc. to be able to show relevant data. There are options to restrict sensitive data at the time of extracting file using extract data dialog box.