Revoke public access to one spefic table

I am new to oracle....lets start with that.  The tables in our database have been added by using a middleware application.  All of our tables have the grantee as public and security is maintained using the middleware application. Currently our users only have access to the database through the middleware application but I want to link the database to an excel spreadsheet but I can not limit the table access from excel.  I also can not limit the table access though oracle because all the tables have public access.  I have tried to revoke select on table_name from public but when I login to a new session I still can view the data in this table.  How can I get around this?