At 13:10 +0000 2003/11/03, Matthew Byng-Maddick wrote:
>On Mon, Nov 03, 2003 at 01:12:26PM +0100, Christoph Kliemt wrote:
>> Matthew Byng-Maddick <exim@???> writes:
>> > On Mon, Nov 03, 2003 at 11:41:30AM +0100, Christoph Kliemt wrote:
>> >> I do it this way: If someone tries to relay, i put the ip in a
>> >> database (postgres) and refuse a connection (acl_smtp_connect) for a
>> >> week or so... it works! :-)
>> > That's a really stupid thing to do. If you misconfigure an MX, or a
>> > client of yours misconfigures an MX to point to you, then you end up
>> > blacklisting innocents.
>> Someone who misconfigures an MX is not innocent.
>
>You misconfigure your MX, they send mail where the MX tells them to, you
>blacklist them. That sounds innocent to me. You're killing the mail of
>the third party, because of your mistake. Not only that, but you're failing
>to let them mail your postmaster, because of your mistake.
>
sorry guys, but I fail to see where exactly the disagreement is. But
of something I am sure, misconfiguring MX could be a type of DOS
attack, although a very bland one. By misconfiguring an MX you indeed
would cause all clients attempting to deliver to the corresponding
domain to be blacklisted by the server to whom the MX points to, if
that server implements the automatic blacklisting policy.
This also points to a possible solution, that is, if someone attempt
to relay first check the MX, if the MXs point to you log the entry
(for further action), if the MXs do not point to you, blacklist them.
More than I care to do (I do not enforce blacklisting based on
attempts) but perhaps something Matthew would accept.
Giuliano (in a good mood because the line is back..)
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