Re: [Exim] Fixing SPF Forward Problem by Reply-to: Hack?

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Autor: Avleen Vig
Datum:  
To: Edgar Lovecraft
CC: exim-users
Betreff: Re: [Exim] Fixing SPF Forward Problem by Reply-to: Hack?
On Sun, Mar 21, 2004 at 08:23:09PM -0600, Edgar Lovecraft wrote:
> I cannot let that slide, even though my opinion has been called nieve.
> Why use SPF when there is a much simpler approach to those examples.
> EVERY ISP should at the very least scan email for viruses before the
> message leaves its relay servers, so how does SPF protect what message
> scanning does not.


Because virus scanners:
  1) always lag BEHIND the latest viruses, anythign from hours to days
  2) virus scanning is *very* expensive both in CPU and financial respects
  3) SPF is significantly cheaper and not only catches the virus example
     but the spam one too


> As to 'direct to MX' this is where EVERY ISP should disallow outbound port
> 25 (SMTP), thus forcing the spam/virus to send either through the relay,
> or to another relay that is on a port different than 25 (wich can be
> easily tracked). So again, how does SPF help?


Here I agree 100%. We (the ISP where I work) does this, but it is only
applicable to those users whose circuits pass directly through the ISP's
network like dial-up or DSL. Cable broadband and satalite does not and
it is much harder to block in this way. Actually because multiple ISP's
can share the same Cable / Sat service, I believe it's near impossible.

> My solution proposed above is easier to implement than SPF, and DOES NOT
> require 'global compliance' to work, as thse ISP's that do allow 'rouge'
> traffic are going to be discredited and 'blacklisted' in their entirety
> until the problems are taken care of.


Before you do that, please figure out how to solve the cable/sat problem
highlighted above.

> Is this inconvienient to those that do not 'pay for the priviladge' of
> running thier own servers (either 'business class connections' or 3rd party
> relay server) yes, but so is SPF, and SPF is less friendly to thses people
> than my solution (but just with SPF my solution does not 'fix' everything).
> Cheers!


It's a minor inconvenience but it's about the same as SPF, no better or
worse. I'll agree that there isn't one final "good" solution.