While the bitcoin network is essentially P2P, one still needs to identify an initial node to connect to. I understand that a method for such initial connections is connecting to known DNS seeds, e.g seed.bitcoin.sipa.be. If a malicious actor were to, hypothetically, redirect this "link" to a seed that points to a different network, where, for example, he has 51% majority, could any damage be caused by this ?
1 Answer
Generally there's some discussion about attacks against the bootstrapping of Bitcoin Core, but there's not a whole lot in terms of being able to defend against it. Fortunately the DNS seeds are only really used on the first launch of the software, the rumoring of peers within the network is used for all subsequent connections.
There's not a whole lot that could be done with gaining this sort of access without a lot of cost beyond just subverting DNS seeds. The clients have an idea of the total amount of work needed for the chain to be valid, so won't be fooled by an entirely new blockchain that has no connection to the real one. Mining with a low hashrate at the tip of the real blockchain is not possible either due to there being a maximum amount the difficulty can drop in each period; you can't simply mine 2 weeks worth of blocks and have the difficulty drop to nearly zero.
Ideally we'd now have the DNS seeds, but the risks they introduce are manageable, the bootstrapping issue isn't unique to Bitcoin, it's something that all P2P networks need to contend with to some degree.
