default iptables rules

[Jimmy Wu]

On 9/15/07, NoOp <glgxg at sbcglobal.net> wrote:
>
> On 09/15/2007 05:02 PM, Jimmy Wu wrote:
> > On 9/14/07, John L Fjellstad <john-ubuntu at fjellstad.org> wrote:
> >>
> >> Peter Garrett <peter.garrett at optusnet.com.au> writes:
> >>
> >> > I have found the simplest way to set up iptables is to start with a
> >> > default "DROP" policy for INPUT
> >>
> >> One thing to note is that if you are ssh into a box, it might not be a
> >> good idea to add this policy first (God knows I've done that a couple
> of
> >> times :-) ).
> >>
> >> --
> >> John L. Fjellstad
> >> web: http://www.fjellstad.org/          Quis custodiet ipsos custodes
> >>
> >>
> >> --
> >> ubuntu-users mailing list
> >> ubuntu-users at lists.ubuntu.com
> >> Modify settings or unsubscribe at:
> >> https://lists.ubuntu.com/mailman/listinfo/ubuntu-users
> >>
> >
> > Thanks all for the responses, especially Peter for your script.
> > Just a few more questions: I don't have any servers running that I know
> of,
> > but I do have samba installed - does that open any ports I should worry
> > about?
> > Also, how do I find out what ports are open?
> > I tried a netstat -l and got a lot of output (which I've attached to the
> > end)
> >
>
> sudo apt-get install nmap
>
> sudo nmap -sV localhost
>
> With samba running these ports will be open:
>
> 139/tcp   open  netbios-ssn Samba smbd 3.X (workgroup:
> nameofyourworkgroup)
> 445/tcp   open  netbios-ssn Samba smbd 3.X (workgroup:
> nameofyourworkgroup)
>
> You can replace localhost with an IP or domain name.
>
>
> Much thanks.  The obvious next question is how to control which ports are
listening or closed.  Also, I've heard of port stealthing on certain
firewall software -- does anyone know what that is?


@Peter Garrett:
I followed the instructions in the IPTABLES HOWTO of the online community
Ubuntu docs, and added the following line to my /etc/network/interfaces
entry for eth0:
pre-up iptables-restore < /etc/network/iptables.up.rules
and it does properly save my iptables rules. (I tested it by flushing the
rules with -F and doing a /etc/init.d/networking restart).  I think this
ensures that the rules are put in place whenever a network connection is up
(I only use eth0)
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