pgsql-bugs(at)postgresql(dot)org writes:
> I can connect to the database with a valid username and with a false
> password. Why ?
No doubt it's because you've got pg_hba.conf set to "trust" ...
passwords aren't checked unless pg_hba.conf specifies a password-
based authentication mechanism. See
http://www.postgresql.org/users-lounge/docs/7.0/postgres/security.htm
regards, tom lane