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> > > > > Anyway, a closed port remains closed whether a firewall is |
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> > > > > running, or not. |
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> > > > |
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> > > > I thought the firewall specified which ports to open/close. |
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> > > |
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> > > Not quite, but we might be running into terminology here. |
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> > > |
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> > > The app that is listening a port opens the port. This has nothing |
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> > > to do with the firewall. The firewall is simply an extra level of |
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> > > checks applied before the packet is allowed thorugh the firewall to |
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> > > be received by the kernel, in the same way that a bouncer allows or |
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> > > disallows the public to enter a club. If the bouncer is off sick, |
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> > > the public gets to walk through the door up to reception, assuming |
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> > > the club is open for business. |
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> > > |
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> > > What Mick was referring to is that if a service is running, it's |
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> > > still going to listen on it's port whether iptables is running or |
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> > > not. So, in the absense of iptables (i.e. your bouncer is off |
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> > > sick), you hopefully have a decent password strategy in use by |
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> > > whatever is actually listening on the box. |
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> > |
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> > So as far as incoming connections are concerned, if there are no |
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> > listening applications, there is no need for a firewall? |
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> |
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> Technically yes. In the real world, it depends. The theory will work if |
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> and only if you can absolutely guarantee that no listening service will |
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> ever be running behind that firewall, and that this will always be true |
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> from here on out till the end of time regardless of who has access to |
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> the machine. |
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> |
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> That's a tall order, and leaves human nature out of it. You might |
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> install a listening app and leave it running in error without realising |
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> the impact of not having a firewall. Someone else might do the same. |
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> |
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> Ubuntu takes the approach you just asked about and it mostly works well, |
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> especially for notebooks on a LAN behind a NATing gateway. If you are |
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> running a network with valuable private information on it, you might |
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> well prefer a belts and braces approach of having a mostly-closed |
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> firewall as well. |
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> |
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> As always, the best solution will vary according to what *you* need |
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|
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On more question, is default the right runlevel in which to run |
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shorewall? It looks like it's one of the last services to start that |
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way. |
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|
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- Grant |
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-- |
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