"bot" hails from the apparently inscrutable "Easten Network Co." of Beijing, China, a.k.a. the same IP(s) as lanshanbot [webmasterworld.com].
I see it running from 22.214.171.124 repeatedly (lanshanbot uses .146, .147, etc.), but it's good you've got it blocked basically by default. Akin to lanshanbot, bot is sneaky -- it'll ask for robots.txt and then completely ignore it.
(Both lanshanbot and bot are also undaunted by 403s so the IP block is on my nuke-via-firewall to-do list.)