[Mimedefang] Blocking Dictionary Attacks
Les Mikesell
les at futuresource.com
Tue Jun 9 10:38:08 EDT 2009
afo cliff wrote:
>>>> Matt Garretson wrote:
>>>>> afo cliff wrote:
>>>>>> @mydomain.com bitbucket
>>>>> You can also do something like this in your virtusertable:
>>>>>
>>>>> @mydomain.com error:5.1.1:550 User unknown
>>>>>
>>>>> Then, you won't need the bitbucket alias.
>>>>> See http://www.sendmail.org/m4/features.html
>
> Yes thanks, I tried that, the down side for me is that it sends a
> "User Unknown" reject notification, which I'm trying to avoid. I
> don't want my server to waste time sending 10,000 rejects to a zombie
> somewhere.
You have that backwards - it's much, much faster to send a '5xx' failure
response in the SMTP conversation before accepting any data. Also, by
accepting, you'll convince the sender that the addresses are legitimate
and they'll end up on lists that are re-used for years - but it is
probably already too late for that.
--
Les Mikesell
lesmikesell at gmail.com
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