*   Maybe no one would be willing to go with np=reject without being able to 
confirm there's no good mail doing that.

Exactly this. As we’ve pushed DMARC across gov.uk we’ve found all sorts of 
interesting things in the reporting we get.

Ta.

I.

--
Dr Ian Levy
Technical Director
National Cyber Security Centre
[email protected]<mailto:[email protected]>

Staff Officer : Kate Atkins, [email protected]<mailto:[email protected]>
Pronouns : he/him

(I work stupid hours and weird times – that doesn’t mean you have to. If this 
arrives outside your normal working hours, don’t feel compelled to respond 
immediately!)

From: dmarc <[email protected]> On Behalf Of Brandon Long
Sent: 12 December 2019 23:38
To: Kurt Andersen (b) <[email protected]>
Cc: IETF DMARC WG <[email protected]>; Scott Kitterman <[email protected]>
Subject: Re: [dmarc-ietf] Comment on draft-ietf-dmarc-psd



On Wed, Dec 11, 2019 at 7:45 AM Kurt Andersen (b) 
<[email protected]<mailto:[email protected]>> wrote:
On Tue, Dec 10, 2019 at 2:13 PM Brandon Long 
<[email protected]<mailto:[email protected]>> wrote:

On Mon, Dec 9, 2019 at 6:27 PM Kurt Andersen (b) 
<[email protected]<mailto:[email protected]>> wrote:
On Mon, Dec 9, 2019 at 4:54 PM Scott Kitterman 
<[email protected]<mailto:[email protected]>> wrote:
On Monday, December 9, 2019 7:41:27 PM EST Brandon Long wrote:

> I'm sure I probably missed this, but couldn't we avoid this question by just 
> mandating no reporting for non-existing organizational domains?  Is that a 
> non-starter?

It's one of the use cases we are trying to cover.  I don't know if that makes 
it a non-starter.

Unless I'm misunderstanding Brandon's suggestion, it seems like you (Brandon) 
are asking if doing no reporting on missing org domains solves the scalability 
problem. *Getting* reports for missing org domains is the main purpose of the 
PSD proposal so it would render the purpose moot.

Hmm, I guess I don't see it that way.

Preventing phishing attacks from 
nonexistent.gov.uk<https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fnonexistent.gov.uk&data=02%7C01%7Cian.levy%40ncsc.gov.uk%7C522306c0a8a84aca4a7308d77f5c5d4b%7C14aa5744ece1474ea2d734f46dda64a1%7C0%7C0%7C637117906987236215&sdata=Be5QRL1NweewdLl2E6UbuliKRWqAEZb0KPS7YW8nn5E%3D&reserved=0>,
 insomuch as DMARC can be used for such, seems way more important than the 
reporting.  Obviously, getting to p=reject without reporting is more 
challenging.  You can certainly have policy without reporting.

While it is very true that receivers may implement validation and possibly 
enforcement without reporting, we could solve the use case of phishing from 
missing org-level domains by the same approach that we can solve it from any 
missing domain - just don't accept mail from such bogus sources. That does not 
help the overseers of a domain realm (org-1, aka LPSD) to tackle takedowns or 
public awareness campaigns against such abuse though.

I mean, that was also true for all DMARC, the point was the owner was asking 
everyone to do that.  If you're saying we should have a different system for 
trying to get everyone to not accept messages from non-existent domains... ok, 
but I'm not sure where that would come from.

Maybe no one would be willing to go with np=reject without being able to 
confirm there's no good mail doing that.  That seems more likely to be true for 
existing large scale branded domains (which I guess 
gov.uk<https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgov.uk&data=02%7C01%7Cian.levy%40ncsc.gov.uk%7C522306c0a8a84aca4a7308d77f5c5d4b%7C14aa5744ece1474ea2d734f46dda64a1%7C0%7C0%7C637117906987246211&sdata=ADl8m4tEnSW2tzuk6dWIVU7sx8Y%2BRUQ%2FS1cffxjsuOU%3D&reserved=0>
 falls into), whereas setting that policy for the newer branded domains 
(.google) and multi-organizational (.bank) seems fine without reporting.

Brandon
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