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Date:      Wed, 24 May 2000 13:07:20 -0500 (CDT)
From:      Mike Silbersack <silby@silby.com>
To:        Steve Shah <sshah@clickarray.com>
Cc:        Olaf Hoyer <ohoyer@fbwi.fh-wilhelmshaven.de>, freebsd-net@FreeBSD.ORG
Subject:   Re: BPF vs. promiscuous mode
Message-ID:  <Pine.BSF.4.21.0005241302190.21535-100000@achilles.silby.com>
In-Reply-To: <20000524092918.B14746@clickarray.com>

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On Wed, 24 May 2000, Steve Shah wrote:

> The messaging stuff is easy to proxy for, and I don't mind doing that.
> Napster I'd block off from the standpoint of bandwidth consumption. And
> now that there is <sigh> legal precidence on schools getting sued for
> crap like that, I'd rather save myself the hassle. There are better battles
> to fight.
> 
> The definate win for NATting would be against the web server folks
> who are serving up commercial stuff and MP3's. Although Napster is
> a ugly problem in that regard. (Today's User Friendly explains why 
> in ugly, ugly detail...)
> 
> Most importantly, it's a case of protecting students from attacks.
> There are (sadly) people out there who still find it amusing to BOINK
> large numbers of Winders machines that aren't patched up. And I
> wouldn't trust most students to keep their boxes patched up.

It may just be simpler to block outgoing connections to napster/etc, and
block incoming connections to port 21/80/137/138/139; then you don't have
to worry about the hassles of proxification.  I guess what you choose
depends on your local policies / etc.  I think 137/138/139 would be a
no-brainer in any case, though.  I've seen a few people become bandwidth
hogs due to scour.net without even knowing it.  (Also, blocking those
ports would stop a good percentage of the windows attacks dead.)

> In the end, there is always a way to get back in. (Tunnels, etc.)
> but just looking at the small handful of people who know how to do
> that means that I still would not have to be overly concerned with
> bandwidth. Of course if I *really* wanted to be a punk, I'd put a 
> rate limitor on outgoing traffic. 
> 
> -Steve

Rate limiting might actually be the most fair solution for the future, as
it's likely napster-like programs are going to evolve to the point where
explicitly blocking them is impossible.  I think something like 16K/sec is
more than acceptable.

Mike "Silby" Silbersack



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