Thanks in large part to our research partnership with the group at Princeton CITP, Let's Encrypt has deployed a system we call multi-perspective validation. We

Thanks in large part to our research partnership with the group at Princeton CITP, Let's Encrypt has deployed a system we call multi-perspective validation. We validate domain control from multiple network perspectives so that an attacker would have to pull off several simultaneously successful BGP attacks in order to hijack our validation. It's not perfect but it makes it very difficult to do. There are other improvements coming that will further improve effectiveness. https://www.cs.princeton.edu/~jrex/papers/multiva20.pdf https://www.cs.princeton.edu/~jrex/papers/multiva20.pdf I believe the Google Trust Services CA recently announced that they have started doing this as well.