[Mimedefang] Rejecting Mails for More Than 3 Unknown Users
Ben Kamen
bkamen at benjammin.net
Tue Mar 27 16:00:09 EDT 2007
imacat wrote:
> On Tue, 27 Mar 2007 08:40:05 -0400
> Joseph Brennan <brennan at columbia.edu> wrote:
>> --On Tuesday, March 27, 2007 13:10 +0800 imacat <imacat at mail.imacat.idv.tw>
>> wrote:
>>> Dear all,
>>> Hi. This is imacat from Taiwan. Is it possible to reject mails for
>>> more than 3 unknown users, to fight against dictionary attacks?
>> Put this in sendmail.mc and generate sendmail.cf. Test it.
>> LOCAL_RULESETS
>> SLocal_check_rcpt
>> R$* $: $1 $| $( arith l $@ $&{nbadrcpts} $@ 3 $)
>> R$* $| FALSE $#error $: 450 Too many bad recipients
>
> That's amazing. I like clean and neat solutions that won't give
> too much possibility for bugs and exceptions.
>
> I shall give it a try. Thank you very much for this. (Though I'm
> still waiting for MIMEDefang to support SMFIP_RCPT_REJ.)
for more fun:
Put this in your sendmail config in domain/.m4 file:
define(`confBAD_RCPT_THROTTLE',`2')dnl
this will slow 'em down too.
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