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
But:

1. couldn’t you “just” (yea yea I know) install a cert on all your devices and force all 443 traffic though a proxy (like some corporate networks do)?

2. (Something I’ve been meaning to get around to trying for a while) default-block outgoing connections unless unless the external host was recently resolved for the corresponding internal host via your internal resolver? That seems like it would kill anything that tries to avoid your ad-blocking resolver. It seems like that might block hard-coded addresses too, but that could be a good thing..

>>labcom+Yz
The biggest problem with 1) is that you lose the ability for your browser to perform checks on the certificate. If the certificate fails, the only option is to deny the connection. (Or fake it and return an error page but that can have unintended consequences.)

And with 2), that would work, though you'd probably want to whitelist port 53 so that you can resolve names in the first place. Sounds like it should be effective, though.

>>Sophir+iI
Those checks are then performed on the MITM device. Instead of an error page the device could return the same sort of page that your browser would otherwise display for you. The connection has been MITM'd after all.