zlacker

>>taubek+(OP)
Here are a few things I do to combat nasty websites:

- blacklists entire domains using wildcards (using an "unbound" DNS resolver and forcing all traffic to my DNS resolver, preventing my browser to use DoH -- I can still then use DoH if I want, from unbound)

- reject or drop a huge number of known bad actors, regularly updated: they go into gigantic "ip sets" firewall rules

- (I came up with this one): use a little firewall rule that prevents any IDN from resolving. That's a one line UDP rule and it stops cold dead any IDN homograph attack. Basically searching any UDP packet for the "xn--" string.

I do not care about what this breaks. The Web still works totally fine for me, including Google's G Suite (yeah, I know).

EDIT: just to be clear seen the comments for I realize I wasn't very precise... I'm not saying all IDN domains are bad! What I'm saying is that in my day to day Web surfing, 99.99% of the websites I'm using do not use IDN and so, in my case, blocking IDN, up until today, is totally fine as it not only doesn't prevent me from surfing the Web (I haven't seen a single site I need breaking) but it also protects me from IDN homograph attacks. Your mileage may vary and you live in a country where it's normal to go on website with internationalized domain names, then obviously you cannot simply drop all UDP packets attempting to resolve IDNs.

>>Tactic+ra
While these are all good practices, killing DoH conclusively on your home network is more difficult than you've made it seem, as ultimately all you can really do is use domain blacklists at your firewall. It's no longer as straight forward as just control port 53 traffic, not like you can realistically shut down 443... Blocking DoH is largely whack-a-mole and I think is only going to get worse as this and similar techniques spread. There are so many sneaky ways to resolve a hostname an app or device can choose to use now.

You can force traditional port 53 DNS protocol traffic to your own resolver with firewall rules, the same doesn't work for DoH. a DoH request to a domain your firewall blacklist doesn't have looks just like ordinary https/443 traffic and will pass unhindered.

>>giobox+yk
DoH uses UDP, not TCP. Unless you're using HTTP3/QUIC, you can block port 443/UDP.

And hey, maybe one day advertisements will be served directly via IP addresses, not domains:)

>>mmsc+cI
There's nothing stopping you just making your own REST API and responding over HTTPS that returns hostname records for any service you build or run - it doesn't even need to use an existing DoH standard. These are exactly the sort of tricks stuff like IoT devices are already using to ensure they can phone home regardless of your network's DNS settings.

DoH is literally just "DNS over HTTPS" (hence the TCP a lot of the time) and you can build this a ton of different ways, including as a basic RESTful API. Local javascript on the page could literally just call any old HTTPS web API to get hostnames resolved, and thanks to HTTPS is much harder to detect, inspect and interfere with than traditional DNS. Fundamentally, a DNS request is a really basic API to implement.

This is why DoH is so hard to conclusively block - its by design to look like "normal" web traffic so bad actors are prevented from manipulating your DNS responses, and the implementation can be done pretty much anyway you want - there are a million different ways to pass a message over HTTPS, and to a firewall they all look like the exact same normal HTTPS traffic if you don't explicitly block the IP or domain serving the DoH.