[exim] Re: heads-up: some spam bots started RCPT flooding

Top Page
Delete this message
Reply to this message
Author: James
Date:  
To: exim-users
Subject: [exim] Re: heads-up: some spam bots started RCPT flooding
On 15/05/2023 10:21, Markus Reschke via Exim-users wrote:

Firstly I thank you for raising this on the mailing list and providing help.

> I moved to a simple ACL rule to drop the connection when the
> first x recipients are rejected:
>
> drop  message = Too many bad recipients
>       condition = ${if and
> {{>{$rcpt_count}{5}}{=={$recipients_count}{0}}}{yes}{no}}


This works, however if a valid address is given (and everything else
about it is acceptable) in the first 5 then recipients_count is not zero
and condition does not trigger I have seen this attempted hack use
abuse@ and postmaster@ which according to RFCs must be valid.

I use:
     condition = ${if and 
{{>{$rcpt_count}{2}}{>{${eval:$rcpt_count-$recipients_count}}{2}}}{yes}{no}}


this allows only 2 bad recipients.

Note I have yet to see this hack use a valid address and not be rejected
for some other reason so $recipients_count has been zero anyway.

--
## subscription configuration (requires account):
## https://lists.exim.org/mailman3/postorius/lists/exim-users.lists.exim.org/
## unsubscribe (doesn't require an account):
## exim-users-unsubscribe@???
## Exim details at http://www.exim.org/
## Please use the Wiki with this list - http://wiki.exim.org/