Be aware of the following changes that introduce incompatibilities with how your existing applications interface with Firebird's security:
Apart from the enhancement this offers to server security, it also isolates the mechanisms of authentication from the implementation.
A non-privileged user can retrieve or modify only its own account and it can change its own password.
If you upgrade an existing installation, be sure to upgrade the security database using the provided script in order to keep your existing user logins.
Before you begin the necessary alterations to commission an existing security database on the Firebird 2.0 server, you should create a gbak backup of your old security.fdb (from v.1.5) or isc4.gdb (from v.1.0) using the old server's version of gbak and then restore it using the Firebird 2.0 gbak.
Important: You must make sure that you restore the security database to have a page size of at least 4 Kb. The new security2.fdb will not work with a smaller page size.
Warning: A simple 'cp security.fdb security2.fdb' will make it impossible to attach to the Firebird server!
For more details see the notes in the chapter on security in the accompanying Release Notes. Also read the file security_database.txt in the upgrade directory beneath the root directory of your installation.
(v.2.1) On Windows, the default authentication mode is Mixed, which allows operating system users with Local Administrator or Domain Administrator group privileges to attach to databases with “blank” Firebird user name and password.
Warning: If you consider this insecure for your network setup, the change the parameter Authentication in firebird.conf.