From owner-freebsd-security Wed Aug 16 23:25:39 2000 Delivered-To: freebsd-security@freebsd.org Received: from sasami.jurai.net (sasami.jurai.net [63.67.141.99]) by hub.freebsd.org (Postfix) with ESMTP id 1808937BBCD for ; Wed, 16 Aug 2000 23:25:30 -0700 (PDT) (envelope-from scanner@jurai.net) Received: from localhost (scanner@localhost) by sasami.jurai.net (8.9.3/8.8.7) with ESMTP id CAA07146; Thu, 17 Aug 2000 02:25:07 -0400 (EDT) Date: Thu, 17 Aug 2000 02:25:06 -0400 (EDT) From: To: Erick Mechler Cc: "Rashid N. Achilov" , freebsd-security@FreeBSD.ORG Subject: Re: deny incoming icmp In-Reply-To: <20000816221521.B23432@sendmail.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Wed, 16 Aug 2000, Erick Mechler wrote: > First you have to enable firewalling code in your kernel. Once you've done > that, the following two ipfw rules should do what you want: > > ipfw add deny icmp from any to any > ipfw add allow icmp from ${oip} to any via ${oif} > > where ${oip} is the IP address of your outside interface, and ${oif} is the > outside interface itself. Ok I was going to make this private but I want this on public record. Look people. You cannot just "flip off" ICMP without understanding the consequences. The above is bad advice. If your going to filter ICMP *do it correctly*. I see way to many post's today suggesting to just filter ICMP entirely. FEH! Read the following URL: http://users.worldgate.com/~marcs/mtu/ And then filter *correctly*. There very few reasons to place an embargo on the entire ICMP protocol. ============================================================================= -Chris Watson (316) 326-3862 | FreeBSD Consultant, FreeBSD Geek Work: scanner@jurai.net | Open Systems Inc., Wellington, Kansas Home: scanner@deceptively.shady.org | http://open-systems.net ============================================================================= WINDOWS: "Where do you want to go today?" LINUX: "Where do you want to go tommorow?" BSD: "Are you guys coming or what?" ============================================================================= To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message