bugtraq - Re: Exploiting Google MX servers as Open SMTP Relays

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Date: Sat, 10 May 2008 12:03:58 -0700 (PDT)
From: Lamont Granquist <lamont@...iptkiddie.org>
To: "Todd T. Fries" <todd@...es.net>
Cc: Michael Scheidell <scheidell@...nap.net>, pablo.ximenes@....edu,
	bugtraq@...urityfocus.com
Subject: Re: Exploiting Google MX servers as Open SMTP Relays


I was getting backscatter SPAM from google and enabled SPF rules in my DNS 
domain along with installing Vbounce in SpamAssassin and it has basically 
all stopped.

SPF specifically addresses the Google bounce issue, since Google 
implements SPF.  When a spammer sends a message to google with a forged 
From: header for my account, Google will lookup my domains SPF record and 
see that the spammers mail sender is not a valid sender for my domain and 
will not send a bounce.

There is some loss of flexibility in enabling SPF (you *must* now send 
e-mail outbound through those approved senders), and it abuses DNS TXT 
records, but it works great for me.  I could care less if it isn't "the" 
solution for everyone on the internet -- but it made all my google 
backscatter spam go away and hasn't caused me any issues.

Vbounce is also useful since it catches all kinds of backscatter from 
other virus scanners and spam scanners and sites that don't implement SPF 
checking.

On Sat, 10 May 2008, Todd T. Fries wrote:
> Oh and btw, unless you have another different issue you are reporting,
> this well documented behavior has been reported before:
>
>  http://rss.slashdot.org/~r/Slashdot/slashdot/~3/266688832/article.pl
>
> *grumble*
> -- 
> Todd Fries .. todd@...es.net
>
> _____________________________________________
> |                                             \  1.636.410.0632 (voice)
> | Free Daemon Consulting, LLC                 \  1.405.227.9094 (voice)
> | http://FreeDaemonConsulting.com             \  1.866.792.3418 (FAX)
> | "..in support of free software solutions."  \  1.700.227.9094 (IAXTEL)
> |                                             \          250797 (FWD)
> \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
>
>              37E7 D3EB 74D0 8D66 A68D  B866 0326 204E 3F42 004A
>                        http://todd.fries.net/pgp.txt
>
> Penned by Todd T. Fries on 20080510 13:04.42, we have:
> | Yes this is very frustrating.
> |
> | The details are not so hard to guess.  Unless this post is different,
> | anyone can send an email to a nonexistent user at a google service and
> | they accept it and bounce back to the envelope recipient. *sigh*.
> |
> | We are going back to the stone age by copying qmails default stupidity.
> |
> | This is doing very much harm.
> |
> | I would even go as far as to say that Google is making a business case for
> | its latest purchase, postini, in a very evil way, every second this proble
> | goes unsolved.
> |
> | *sigh*
> | --
> | Todd Fries .. todd@...es.net
> |
> |  _____________________________________________
> | |                                             \  1.636.410.0632 (voice)
> | | Free Daemon Consulting, LLC                 \  1.405.227.9094 (voice)
> | | http://FreeDaemonConsulting.com             \  1.866.792.3418 (FAX)
> | | "..in support of free software solutions."  \  1.700.227.9094 (IAXTEL)
> | |                                             \          250797 (FWD)
> |  \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
> |
> |               37E7 D3EB 74D0 8D66 A68D  B866 0326 204E 3F42 004A
> |                         http://todd.fries.net/pgp.txt
> |
> | Penned by Michael Scheidell on 20080510  9:55.32, we have:
> | |
> | |
> | | > From: <pablo.ximenes@....edu>
> | | > Date: 7 May 2008 20:37:46 -0000
> | | > To: <bugtraq@...urityfocus.com>
> | | > Subject: Exploiting Google MX servers as Open SMTP Relays
> | | >
> | | >
> | | > Vulnerability Report:
> | | >
> | | > As part of our recent work on the trust hierarchy that exists among email
> | | > providers throughout the Internet, we have uncovered a serious security flaw
> | | > in Ggoogle's free email service, Gmail.
> | | >
> | | > Disclosure:
> | | > We have contacted Google about this issue and are waiting for their position
> | | > before releasing further details.
> | | >
> | |
> | | Don't hold our breath.. I have tried to get them to close this very hole for
> | | maybe a year now.
> | |
> | | (see/'google' for posts in bugtraq and spamassassin users group showing
> | | headers from unrelated domains sending spam through google mail servers..
> | | They ignore the emails to abuse@...gle.com)
> | |
> | |
> | | --
> | | Michael Scheidell, CTO
> | | >|SECNAP Network Security
> | | Winner 2008 Network Products Guide Hot Companies
> | | FreeBSD SpamAssassin Ports maintainer
> | |
> | | _________________________________________________________________________
> | | This email has been scanned and certified safe by SpammerTrap(r).
> | | For Information please see http://www.spammertrap.com
> | | _________________________________________________________________________
>