I am starting a new project for small clients (mostly single-user),
and I want to choose Firebird/IBO because it is affordable and has
some database security. The problem is how can I setup a database
that is secure(no one can open this database except a certain user
name and password).
I can setup a certain user name and password, but then the user can
override my security by installing isc4.gdb which will allow him to
access everything using SYSDBA user name. (right?)

Any suggestions or comments?