Overall REMOTE_HOST is grossly inefficient as it forces a reverse DNS lookup which can burn a lot of time opposed to simply blocking by IP range.
Good to know!
I've already got a whitelist reverse DNS checker up for the primary search engines, so if I rewrote that to boot the pest(s) I should be OK.
Looks singular to me ;)
1 really bad one, that's almost un-bannable at this point; every method I've tried thus far seems futile. As soon as I block a range, it comes back with another range... always has the same hostname, though.