[dns-operations] NXDOMAIN rewriting by lying resolvers (Was: new public DNS service: 9.9.9.9

[Andreas Teuchert]

On Wed, Nov 22, 2017 at 09:27:15PM +0100, Stephane Bortzmeyer wrote:
> Which AS? On AS 3320, I indeed see NXDOMAIN rewriting. But a majority
> of RIPE Atlas probes (may be most of them are in proper networks, with
> their own resolvers) see the honest answer:
> 
> % atlas-resolve -r 100 --as 3320 gwfhjdsyfhdsfgsyjfgshgfghqf56546FDRRFG.com
> [104.239.213.7 198.105.244.11] : 1 occurrences 
> [62.138.238.45 62.138.239.45] : 22 occurrences 
> [ERROR: NXDOMAIN] : 75 occurrences 
> Test #10290686 done at 2017-11-22T20:19:15Z

It's enabled by default at least for their residential customers in
Germany, which might all be in AS 3320.

It's possible to opt-out of it, so maybe some of the probes that see an
honest answer are in networks where the customer decided to do that. I
would assume that the majority of people who put an Atlas probe in their
network also would opt-out of NXDOMAIN rewriting.

Kind regards,

Andreas