securing Ubuntu and firewall

[H.S.]

John Richard Moser wrote:
> you don't need a firewall unless you installed something nasty.  Ubuntu
> doesn't open ports by default on the outside.

Can somebody else confirm this? I personally don't think that is true.
When I checked using "iptables -nvL" command on my friend's computer,
his INCOMING, FORWARD and OUTGOING policies were all ACCEPT. The system
is relatively a new install of Ubuntu. So it appears all ports were
actually left open since the installation.

Moreover, I would rather have a firewall no matter if I have "nasty
programs" (whatever that means) or not. It is just being cautious.

regards,
->HS