I've seen spam with List-ID: headers, but I don't think they were of the type I
described. If messages that (look like they) come from mailing lists are less
likely to be blocked by filters (whether this is because of DKIM or for some
other reason), I'm sure spammers will one day make use of it.
To me this means two things:
a) as a receiver (i.e. filter) you should never second guess why a DKIM
signature is broken (I don't think anyone ever suggested one should);
b) as a sender, if your mail is so important that it should be discarded if the
DKIM signature is broken, don't send it through systems that are likely to
break it.
Martijn.
-----Original Message-----
From: Dave CROCKER [mailto:dcrocker(_at_)bbiw(_dot_)net]
Sent: 04 August 2010 18:35
To: Martijn Grooten
Subject: Re: [ietf-dkim] Clarifying DKIM (etc.) expectations for
mailing lists in the face of digests
That sounds like a theoretical attack. Are there examples of this
being done in
the wild? Do the examples demonstrate actual utility?
d/
On 8/4/2010 10:29 AM, Martijn Grooten wrote:
What is the security model that makes this expectation of
preservation
important
and reasonable, given that it is so easily and whimsically violated
by
a common
recipient-selectable setting?
There's a scenario where a spammer/phisher sets up a mailing list,
adds a bunch of addresses to the list and then sends a message with a
paypal.com From: address through the list. The DKIM signature will
obviously be invalid, but a MTA/spam filter won't be able to decide
whether this is because the message didn't really come from Paypal, or
because it did but the mailing list broke it.
Martijn.
Virus Bulletin Ltd, The Pentagon, Abingdon, OX14 3YP, England.
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Dave Crocker
Brandenburg InternetWorking
bbiw.net
Virus Bulletin Ltd, The Pentagon, Abingdon, OX14 3YP, England.
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