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by jagged-chisel 893 days ago
They can't redirect things going to localhost. But how does your local resolver talk other authoritative DNS servers? UDP on port 53. The instant that kind of packet hits your ISP, it's not routed outside their network and is answered by their DNS.

Unless you have DNS-over-HTTPS.

2 comments

Well, I didn't know they did that. They'd have to use a packet filter to do that; in the normal case, I send my UDP query to the authoritative server via its IP address, and if my ISP doesn't forward the query, then it's not providing internet service, it's simulating it. My resolver respects DNS signing, so I think I'd get errors rightaway if my ISP tried to substitute a forged answer.

My (niche) ISP is rather benevolent; as far as I'm aware they don't block at all, and they brag about providing "real internet service". At any rate, I'm not aware that my recursive resolver has ever encountered an answer that was forged by my ISP.

> They'd have to use a packet filter to do that

Indeed they would.

> My resolver respects DNS signing…

I’m not honestly certain how big of a hurdle this is. I would figure that if a site is to be blocked, then the ISP substitutes their own “authoritative” response, which would include cryptographic signing details (even pretending their public key is the official one.)

> My (niche) ISP is rather benevolent …

I think most are. In my market, even the big guys haven’t done this, though I have heard about it happening in larger markets when big ISPs are up to no good (like inserting ads or whatever.)

Your local resolver would be configured to use DoT to Connect to whichever upstream server you choose.

This is a two line configuration in unbound and does not require creating and maintaining your own certificates.

9.9.9.9 is free or you can use nextdns as your upstream and get the benefits of a pi-hole in the cloud.

Everyone should do this.

Or https://mullvad.net/en/help/dns-over-https-and-dns-over-tls

Has the same benefits and works Triple-A-superplusgood.