Protect firebird database

Good morning, I'm developing a C # winforms system with the firebird 3 database that will work on the internal network a company, the same follows a client x server scheme, where it will have a server application with the DB and the clients will access the server database. The problem is that after several searches, I have not found a viable solution to protect the file from the database, knowing that even though I change the default password of the SYSDBA user a malicious user copy the database file to another server with any password and it will have access to any structure, including the data. How could I do to add an extra level of security to my database?