From owner-freebsd-net Wed Jan 24 7:35:50 2001 Delivered-To: freebsd-net@freebsd.org Received: from dustdevil.waterspout.com (unknown [64.64.82.228]) by hub.freebsd.org (Postfix) with ESMTP id 5CEAB37B400 for ; Wed, 24 Jan 2001 07:35:33 -0800 (PST) Received: (from csg@localhost) by dustdevil.waterspout.com (8.11.1/8.11.1) id f0O5X5E00291; Wed, 24 Jan 2001 00:33:05 -0500 (EST) (envelope-from csg) Date: Wed, 24 Jan 2001 00:33:05 -0500 From: "C. Stephen Gunn" To: Renaud Waldura Cc: Patrick Bihan-Faou , freebsd-net@FreeBSD.ORG Subject: Re: How to send arp request with no other traffic Message-ID: <20010124003305.B231@waterspout.com> References: <006901c085ae$fae9bd80$0402010a@biohz.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <006901c085ae$fae9bd80$0402010a@biohz.net>; from renaud@waldura.com on Tue, Jan 23, 2001 at 06:40:14PM -0800 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Tue, Jan 23, 2001 at 06:40:14PM -0800, Renaud Waldura wrote: > An amusing trick to populate the ARP table is to ping the broadcast address. > Even if hosts do not reply to your ping packet (typically, Windows > machines), they are entered in the ARP table. > > You still have to send a single packet, but it does all the work. You can't really assume this will work. FreeBSD has a sysctl to disable responses to broadcast/multicast ICMP-echo requests. Exploitation of this "feature" is the basis for several denial of service attacks. Spoof the origin address to an layer-3 broadcast address and voila, amplified responses. :-( - Steve -- C. Stephen Gunn | Waterspout Communications, Inc. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message