From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] OpenBSD Networking-related randomization port Date: Fri, 28 Jan 2005 10:18:25 -0800 Message-ID: <20050128101825.388990a0@dxpl.pdx.osdl.net> References: <1106932637.3778.92.camel@localhost.localdomain> <20050128174046.GR28047@stusta.de> <1106934475.3778.98.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: netdev@oss.sgi.com Return-path: To: Lorenzo =?ISO-8859-1?B?SGVybuFuZGV6IEdhcmPtYS1IaWVycm8=?= In-Reply-To: <1106934475.3778.98.camel@localhost.localdomain> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Fri, 28 Jan 2005 18:47:55 +0100 Lorenzo Hern=E1ndez Garc=EDa-Hierro wrote: > El vie, 28-01-2005 a las 18:40 +0100, Adrian Bunk escribi=F3: > > On Fri, Jan 28, 2005 at 06:17:17PM +0100, Lorenzo Hern=E1ndez Garc=ED= a-Hierro wrote: > > >... > > > As it's impact is minimal (in performance and development/maintenan= ce > > > terms), I recommend to merge it, as it gives a basic prevention for= the > > > so-called system fingerprinting (which is used most by "kids" to kn= ow > > > how old and insecure could be a target system, many time used as th= e > > > first, even only-one, data to decide if attack or not the target ho= st) > > > among other things. > > >... > >=20 > > "basic prevention"? > > I hardly see how this patch makes OS fingerprinting by e.g. Nmap=20 > > impossible. >=20 > That's an example, as you can find at the grsecurity handbook [1]: >=20 > "The default Linux TCP/IP-stack has some properties that make it more > vulnerable to prediction-based hacks. By randomizing several items, > predicting the behaviour will be a lot more difficult." No it just changes the fingerprint table. "Hmm, this looks like a newer generation system, must be OpenBSD or Linux". > "Randomized IP IDs hinders OS fingerprinting and will keep your machine > from being a bounce for an untraceable portscan." >=20 > References: > [1]: http://www.gentoo.org/proj/en/hardened/grsecurity.xml This is a very transitory effect, it works only because your machine is then different from the typical Linux machine; therefore the scanner will go on to the next obvious ones. But if this gets incorporated widely then the rarity factor goes away and this defense becomes useless. --=20 Stephen Hemminger