> Is it possible to use the CONNECT event of the database
> triggers to catch failed attempts to log in to a database?
> Maybe only successful logins triggers the trigger?

Take a look at the release notes for FB v2.5 and the
section on AUTONOMOUS TRANSACTION... it gives an example
that seems to be exactly what you want. (I presume it
works, I've not tried it myself.)

--
Geoff Worboys
Telesis Computing