Thanks for posting this!
I was wondering if you have a suggestion of how an attack like this can be detected through monitoring and what metrics would be useful to keep track of. I run a couple of “honeypot“ monitoring nodes as part of my peer-observer: A tool and infrastructure for monitoring the Bitcoin P2P network for attacks and anomalies and while I don’t suspect they’ll be attacked with a BGP attack, it could be useful to use some Bitcoin Core external monitoring tool that e.g. periodically traceroutes peers and collects information about reachabillity, AS path length, … to have more real-world data before implementing it in node software.