Hi...
Paul has quote a good point here. I would like just to change the senario a
little bit. Lets blame the cause of this (should it ever happen), on bad
administration, unauthorised access to the servers, or user maintained email
aliases, but consider the following spamming environment....
Two accounts, say account A, and account B. Now lets look at the loop :)
Account A forwards mail to Account B, ASWELL as spam@???
Account B forwards mail to Account A, ASWELL as spam@???
.forward would look like:
accountb@???
spam@???
While none of the accounts has to be located on the same machines or
anything as such, spam@??? is going to get a awefully lot of mail,
especially should there be added a 1MB attachment to the email that will
"infinately?" loop through Accounts A and B. For every successfull loop,
spam@??? gets 2 email messages. What happens when you put in 5
addresses in the loop? or even 10? 10MB of email, through one loop, and
then you keep it running for a few days, and you can even take out complete
servers with this, should hard drive space run out on the server (1GB of
email in one mailbox?). Something which can be quite destructive hey? Or
is it perhaps allready protected?
... Just thought I'd share this piece of information with you all. It is
most probably known, but quite a huge ammount of spam can be generated from
it, and with the talk of mail loops, I just thought I'd drop a note and add
this to the discussion :)
Regards
Chris
----- Original Message -----
From: "Vadim Vygonets" <vadik@???>
To: "Exim Users" <exim-users@???>
Sent: 20 December 1999 04:54
Subject: Re: [Exim] Stopping loops
> Quoth Paul Walsh on Mon, Dec 20, 1999:
> > Local user X.YZ@??? has a Hotmail address X_YZ@???
> > Within MS Outlook on their PC the user sets up Out of Office Assistant
to
> > forward all mail to X.YZ@??? (note they've got the address
wrong).
> > Mail to X.YZ@??? gets redirected by Outlook to X.YZ@???.
> > Hotmail rejects the message because of a non-existant address and sends
it
> > back to X.YZ@??? which gets redirected to hotmail ad infinitum
>
> First, Hotmail should generate bounces with empty return path <>.
> Second, it should not generate bounces for messages whose return
> path is <> (empty). But I think that's not the problem.
>
> Probably the problem is that the Outloop Out of Office
> Assistant[tm] changes the return path of the message when
> redirecting it to Hotmail.
>
> > Question is: What can be done within Exim to either a) stop this
happening
>
> Make the assistant redirect messages without changing the return
> path. In this case, Hotmail's bounces will go to the original
> recipient. LART MICROS~1 or stop using Outloop and use .forward
> files instead.
>
> The quick solution is to change the said luser's Outloop
> configuration, of course.
>
> > or b) queue messages for, say, hotmail.com and only process them every
few
> > hours?
>
> Hmm. That's tricky. You can probably do it using custom
> routers.
>
> Vadik.
>
> --
> Prof: So the American government went to IBM to come up with a data
> encryption standard and they came up with ...
> Student: EBCDIC!
>
>
> --
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