Date: Thu, 16 Oct 2008 10:59:41 -0700 From: Jeremy Chadwick <koitsu@FreeBSD.org> To: RW <fbsd06@mlists.homeunix.com> Cc: freebsd-questions@freebsd.org, Luke Dean <LukeD@pobox.com> Subject: Re: I've just found a new and interesting spam source - legitimate bounce messages Message-ID: <20081016175941.GB16235@icarus.home.lan> In-Reply-To: <20081016173807.64d0f24e@gumby.homeunix.com.> References: <20081016090102.17qwm4xcs6f4so8ok@intranet.casasponti.net> <20081016145255.GA12638@icarus.home.lan> <48F75A88.1000507@infracaninophile.co.uk> <alpine.BSF.2.00.0810160846040.473@border.lukas.is-a-geek.org> <20081016173807.64d0f24e@gumby.homeunix.com.>
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On Thu, Oct 16, 2008 at 05:38:07PM +0100, RW wrote: > On Thu, 16 Oct 2008 08:54:55 -0700 (PDT) > Luke Dean <LukeD@pobox.com> wrote: > > > > > > > On Thu, 16 Oct 2008, Matthew Seaman wrote: > > > > > Until the wonderful day that the entire internet abides by these > > > rules[*], use > > > of technologies like SPF and DKIM can discourage but not entirely > > > prevent the spammers from joe-jobbing you. > > > > I just started getting these bouncebacks en masse this week. > > My mail provider publishes SPF records. > > SPF increases the probability of spam being rejected at the smtp > level at MX servers, so my expectation would be that it would exacerbate > backscatter not improve it. Just a side comment for added clarity: this ultimately depends on how the mail server administrator implemented SPF. For example, our mail servers *do not* do SPF lookups at the SMTP level (e.g. in postfix) because 1) the added complexity is not worth it, and 2) spammers are now hijacking DNS. Instead, our servers use SPF in SpamAssassin, subtracting from the spam probability score if an SPF record is found and matches appropriately. -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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