>It seems unlikely to me that the DNS client has the sophistication to know that it's not Google's 8.8.8.8 that it's talking to I don't know much about DNS but

>It seems unlikely to me that the DNS client has the sophistication to know that it's not Google's 8.8.8.8 that it's talking to I don't know much about DNS but based on what I do know I would think this to be trivial(?). All you'd need to do is make a request for a domain that doesn't exist. Something like "is-this-google-dns-im-connecting-with.google" or <salted hash of current timestamp>.com. Google DNS could be coded to respond accordingly. So no DNS response, or not the response you were expecting = not Google DNS.