Date: Fri, 5 Mar 2010 11:10:03 -0600 From: John <john@starfire.mn.org> To: Matthew Seaman <m.seaman@infracaninophile.co.uk> Cc: Matthias Fechner <idefix@fechner.net>, freebsd-questions@freebsd.org Subject: Re: Thousands of ssh probes Message-ID: <20100305171003.GA18881@elwood.starfire.mn.org> In-Reply-To: <4B913983.30900@infracaninophile.co.uk> References: <20100305125446.GA14774@elwood.starfire.mn.org> <4B910139.1080908@joseph-a-nagy-jr.us> <20100305132604.GC14774@elwood.starfire.mn.org> <F4960422-5F59-4FF4-A2E4-1F0A4772B78B@olivent.com> <20100305154439.GA17456@elwood.starfire.mn.org> <4B912ADC.1040802@infracaninophile.co.uk> <4B91375A.4020503@fechner.net> <4B913983.30900@infracaninophile.co.uk>
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On Fri, Mar 05, 2010 at 05:04:03PM +0000, Matthew Seaman wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 05/03/2010 16:54:50, Matthias Fechner wrote: > > Hi, > > > > Am 05.03.10 17:01, schrieb Matthew Seaman: > >> table <ssh-bruteforce> persist > >> [...near the top of the rules section...] > >> block drop in log quick on $ext_if from<ssh-bruteforce> > >> > >> [...later in the rules section...] > >> pass in on $ext_if proto tcp \ > >> from any to $ext_if port ssh \ > >> flags S/SA keep state \ > >> (max-src-conn-rate 3/30, overload<ssh-bruteforce> flush global) > >> > > > > that is dangarous, if you use subversion over ssh you will sometimes get > > more then 10 requests in 30 seconds. > > That means you will also block users they are allowed to connect. > > Yes. Almost all of the time I use this I've also had a ssh-whitelist > table -- addresses that will never be blocked in this way. Like this: > > table <ssh-bruteforce> persist > table <ssh-whitelist> const { \ > 81.187.76.160/29 \ > 2001:8b0:151:1::/64 \ > } persist > > block drop in log quick on $ext_if from <ssh-bruteforce> > > pass in on $ext_if proto tcp \ > from <ssh-whitelist> to $ext_if port ssh \ > flags S/SA keep state > > pass in on $ext_if proto tcp \ > from !<ssh-whitelist> to $ext_if port ssh \ > flags S/SA keep state \ > (max-src-conn-rate 3/30, overload <ssh-bruteforce> flush global) > Ah. I see. That's clever. Rather than "overriding" the bruteforce list, which would require getting rid of "quick", you use whitelist to prevent things from ever going into the bruteforce table. Nice! I have just switched to pf from ipfw, so I am still learning the nuances and style points. -- John Lind john@starfire.MN.ORG
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