<span class="md_update">Update:</span> Added some remarks about what DNS RPZ actually is, what my objective is and what the outcome will be.
A friend of mine and I tried to play w/ RPZ and knot yesterday and gravely failed. The fact that knot as well as RPZ had been new to us didn't help. Discussing the failure later that night I remembered that I was already doing something similar at home for adblocking at the DNS level instead of every application on every client. In some way this is also DNS RPZ.
DNS RPZ is something that could be described as DNS firewalling and is described by wikipedia as follows:
Domain Name Service Response Policy Zones (DNS RPZ) is a method that allows a nameserver administrator to overlay custom information on top of the global DNS to provide alternate responses to queries. It is currently implemented in the ISC BIND nameserver (9.8 or later). Another generic name for the DNS RPZ functionality is “DNS firewall”.
My main objective is to block ad networks and malware sites (e.g. command and control) on the DNS level for all devices without them having to install adblockers or stuff. So if someone tries to access a blacklisted site, say domain.tld the client will get a NXDOMAIN as an answer instead of the real IP address. As I can't keep up with the domains I also want to leverage some of the OSINT feeds available. Currently I have roughly 16k domains blacklisted.