Re: [exim] ACL filtering

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Autor: Always Learning
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A: Exim Users
Assumpte: Re: [exim] ACL filtering

W B Hacker wrote on Fri, 23 Apr 2010 14:38:13 -0400.

> In about 26 countries now, I've always tried to at least drive on the same side
> of the road as the 'locals' do.


Trying and actually succeeding are sometimes different particularly at
night, when one is tired and after a few alcoholic drinks.

The problem manifests itself when the road is empty, or one is turning a
corner or there is no physical central barrier.

The problem for me is both sides of the road can appear 'normal' to
drive upon. In the 10 (that is all I can remember at present) countries
I have driven in only two, NL and GB, have ever presented a problem for
me on which side of the road to drive. Luckily for everyone, including
myself, I quickly got on the correct side of the road.

> Indeed, SA should be your *last* line of defense. But Exim has all the tools
> built-in for the several barreirs ahead of it. no need to reinvent all that.


Agreed.

> > 4. Yes my pattern matching is indeed 'simplistic'. What can one
> > realistically expect from a brand new Exim user of just 6 months
> > experience of Exim who implemented his 'simplistic' solution with just 3
> > months part-time knowledge ?
> >
>
> Blood in my mouth from biting my tongue...?


Please no violence here. We are peaceful and civilised Exim fans.
Although we may not implicitly invite criticism we do accept it
especially when it is constructive :-)

> WHEREAS..
>
> EITHER a built-in Exim rDNS test OR any number or about a hundred and fifteen
> available RBL calls, dynamic or otherwise, would have found Martin's server
> clean and pristine. MANY of those RBL's would also have blocked the zombots on
> dynamically-assigned ISP pools that *seems* to be the actual object of your
> original exercise.


Does RBL means a type of DNS look-up for blacklisted domains and/or IP
addresses ? I block the worse IP addresses with iptables although I
could add a 'hosts.deny' file to the Exim configuration.

By rDNS do you mean one of my existing tests like this one ?


########################
#                      #
#  MAIL SERVER CHECKS  #
#                      #
########################


deny    message       = [C04] Your mailserver is misconfigured. HELO =
$sender_helo_name; IP host name = $sender_host_name
        !verify       = helo


deny    message       = [C05] Your mailserver is misconfigured. Invalid
Host Reverse Lookup. MsgX
        !condition    = ${if match{$sender_helo_name}{XXXXXX}}
        !verify       = reverse_host_lookup


> It is all well and good to reinvent the wheel if you are learning something from
> that.


The 'wheel' is Exim and my learning experiments are examining different
patterns of spokes to effectively resist the spam I experience. So far I
have been successful.

> But you are no longer so doing.


Really ? Shall I email you my ACL configuration ?

> You've now become fixated on perl-as-a-method instead of the nature of the
> original problem.


No. I am augmenting the defences with a dash of Perl's RegExp but the
fundamental defences depend on basic Exim. Together they appear to be
doing a first-class job for me.

> Go Ogle S.I Hayakawa's citation about left-door syndrome or the famous pike and
> minnows experiment. That fish just 'knows what he knows', and will starve to
> death in the midst of plenty. For 'plenty' read 'this list archives' if not the FM.


Just because I have dabbled, now successfully I hope, in a tiny dash of
elementary Perl it does not mean I have abandoned the core facilities of
Exim :-)

Perl has similarities with PHP (the Die being the most noticeable to the
casual browser, some others being 'x .= y' and the construction of 'If'
statements particularly the types of brackets). The on-line guide calls
'%' a 'hash' when I have always understood 'hash' to be '#'.


Regards,

Paul.

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