Currently Tableau provides row level security, but doesn't cater to column or cell level security.
By column level security, I mean to create a column level filter at the datasource which can be published on the server. And any user creating a new workbook using this datasource should be exposed only to the dimensions/measures that he/she has access to, according to the column level filter configured.
For example - I don't want to show the column "Employee" for a particular User. I know that it is possible to restrict all data for the 'Employee' column through row level security. But I would like to hide the entire column itself so it is not available for a specific User.