Re: [dane] SMTP STARTTLS stripping in the wild

Viktor Dukhovni <ietf-dane@dukhovni.org> Fri, 14 November 2014 00:52 UTC

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Date: Fri, 14 Nov 2014 00:52:53 +0000
From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Subject: Re: [dane] SMTP STARTTLS stripping in the wild
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On Fri, Nov 14, 2014 at 12:43:13AM -0000, John Levine wrote:

> >https://www.eff.org/deeplinks/2014/11/starttls-downgrade-attacks
> 
> This is an anti-spam measure on port 25 traffic on a few mobile
> networks.  I expect there aren't a lot of copies of Postfix running
> on mobile devices.  For all those other mobile users, if they're
> configured correctly they're submitting over port 587 or 465, and
> nobody tries to filter that.

Indeed most such configurations are likely to have similarly mundane
explanations.  I used Paul's message as an excuse for a marketing
message, but forgot to voice my skepticism as to whether this is
an actual attack at work.

I am far more curious about what happened to Google's outbound
TLS mail stats around Oct 14th:

    https://www.google.com/transparencyreport/saferemail/

but this seems likely to remain a mystery.  Perhaps some large peer
botched their TLS settings?

-- 
	Viktor.