Questions from a Newbie

Hi everyone!

I really am a newbie to Postgres, and I have few questions... mainly
security orientated, which I'm hoping I can get a definitive answer on.

1) listen_addresses in postgresql.sql - The documentation states that;

"...The value takes the form of a comma-separated list of host names
and/or numeric IP addresses. The special entry * corresponds to all
available IP interfaces. If the list is empty, the server does not
listen on any IP interface at all, in which case only Unix-domain
sockets can be used to connect to it. The default value is localhost,
which allows only local "loopback" connections to be made. This
parameter can only be set at server start."

I'd like to be able to allow all users on a particular subnet to connect
to the server using PGAdminIII and originally set the variable to:

listen_addresses = 'localhost, 192.168.1.*'

This didn't allow the server to start, so I assume this is incorrect.
Is there any way that this can be done?

2) How do you set the default 'postgres' Login Role to have a password?
 I did what I thought was the correct way in PgAdmin to assign it a
password, and resultant code in the SQL pane does seem like it has an
MD5 password assigned to it, but our security scanning software still
assures me that, "Your PostgreSQL database is not password protected.
We could log in as the user 'postgres'."

Any help on either or both questions would be greatly appreciated!

Thanks

John