I have seen several threads related to protecting a database on a PC where
users have access.

I found a simple solution on a Windows XP PC.
1- Create a user with Admin privileges on the PC
2- Modify the service to run using the new user.

Logon on the PC as this new user and use Windows to encrypt the database and
security.fdb files.

The only drawback is that you will not be able to use the local database
access method.

This scheme prevents unauthorized copying of the database and installation
on another PC on which another firebird instance is running.