It seems like there are lots of ways to prevent man in the middle attacks. I've read many on here and on the rest of the internet. According to wiki you need a secure channel as well to completely safeguard against it. I have two questions in regards to preventing it in the real world.
Does the US government monitor 100% of the lines dug in the US? Obviously (hopefully) data centers are secured but what is there to stop someone from driving out into the desert and physically tapping into a line?
In that scenario, is there anything that can be done by two nodes to detect someone started eaves dropping? (Maybe more of a physics question?) Are there any protocols like this already?
This question is in the scope of public key cryptography because if you have a secure channel you can just exchange a new key as needed.