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Date:      Fri, 22 Jun 2001 22:23:30 -0300 (ART)
From:      Fernando Gleiser <fgleiser@cactus.fi.uba.ar>
To:        alexus <ml@db.nexgen.com>
Cc:        <freebsd-security@FreeBSD.ORG>
Subject:   Re: disable traceroute to my host
Message-ID:  <20010622221554.K5703-100000@cactus.fi.uba.ar>
In-Reply-To: <006a01c0fb6b$2d64d830$9865fea9@book>

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On Fri, 22 Jun 2001, alexus wrote:

> is it possible to disable using ipfw so people won't be able to traceroute
> me?

I don't know if it is posible with ipfw, but with ip filter you can add
a rule to block any packets with ttl=1:

block in log quick on xl0 ttl 1 proto ip all

That will stop windows traceroute (icmp based) as well as unix traceroute
(udp based).

Unix traceroute uses udp packets with destination port > 33434, but this can
be changed. As far as I know, the only way to stop traceroute is to drop
any packet with ttl=1. This might block legitimate trafic, but I haven't
seen any packet in the wild with ttl=1 wich was not a traceroute.


Hope this helps.
			Fer



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