Date: Sat, 23 Jun 2001 14:34:19 +0300 From: Peter Pentchev <roam@orbitel.bg> To: Fernando Gleiser <fgleiser@cactus.fi.uba.ar> Cc: alexus <ml@db.nexgen.com>, freebsd-security@FreeBSD.ORG Subject: Re: disable traceroute to my host Message-ID: <20010623143419.A29940@ringworld.oblivion.bg> In-Reply-To: <20010622221554.K5703-100000@cactus.fi.uba.ar>; from fgleiser@cactus.fi.uba.ar on Fri, Jun 22, 2001 at 10:23:30PM -0300 References: <006a01c0fb6b$2d64d830$9865fea9@book> <20010622221554.K5703-100000@cactus.fi.uba.ar>
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On Fri, Jun 22, 2001 at 10:23:30PM -0300, Fernando Gleiser wrote: > 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. This shall only stop traceroutes destined for this particular machine. If you tried this on a firewall/gateway machine, it would block the response from the gateway itself, but the internal machines would still respond. The response from Igor Podlesny in the thread contains a much more effective approach, which might block a bit too much, but it would certainly block traceroutes. Oh and BTW, blocking all packets with ttl=1 could block some legitimate packets that have simply gone down the long and winding road, and stopped at too many auberges to rest along the way :) G'luck, Peter -- If wishes were fishes, the antecedent of this conditional would be true. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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