Re: Distributed Firewall

[Joerg Over <over () dexia de>]

Am 15:12 23.04.2003 +0100 teilte Kendric mir folgendes mit:
->Hi, just wondering if any of you guys heard of this concept of
distributed
->firewall? I have done some research on it and found it to be
quite a
->wonderful concept into bringing the firewall platform to each
client/server
->end with a central management policy. In other words, it is
like having a
->personal firewall on each individual machine, but centrally
managed by a
->remote management console. In this way, we will not have to put
any trust
->even on the machines on the intranet. Any comments?

I just evaluated NICs with embedded firewall for our company,
with which a hardware based distributed fw can be made/managed.
It so very much depending on the environment you're deploying
them that it's hard to generally tell what use those are, but
some things should be considered:

As for sniffing prevention/egress filtering:
IMHO on that topic they're almost useless. You can always get
around them by just plugging in another NIC (if you have admin
rights on the station) or just plug the cable into a laptop you
bring in, and egress filtering and sniffing prevention are gone.
Similar is valid for software pfws. To enforce egress filtering
even in that setting, you could use routers and switches with a
tight policy on mac adresses and/or vlans, but then again that
can be circumvented (setting the ip/mac on the adapter, other
ways of circumventing vlans, arp spoofing et al), and if it
couldn't, that strict environment alone would be sufficient; no
need for the nics then.

As for ingress filtering:
In this situation a distributed fw can be very powerful. Insofar
as ingress filtering mainly protects the filtered station it's
valuable, but not what you intended.

In summary I'd believe that if you don't trust your intranet,
don't trust it. Meaning: protect your servers (or, generally,
valuable systems under your control) and watch for intrusions. I
wouldn't know a way to force that trust into an intranet in a way
that the (imo rather minor) improvement on the security end isn't
outweighed by the administrative overhead.

This, of course, IMHO and YMMV, and one can easily imagine a
surrounding where every bit of improved security counts enough to
warrant the work, or where more physical security enforces the
use of the firewall on the station end.


hth, jo

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