I had a few IPs in the range 7 - 11 hit by something in June - only minor hits but your posting brought them to my notice. I've now blocked the range 100.43.81/24 - can't block the whole IP range because there are real (US) yandex bots on 220.127.116.11 - 18.104.22.168.
can't block the whole IP range because there are real (US) yandex bots on 22.214.171.124 - 126.96.36.199.
Sure you can.
You block the whole range then punch holes in the firewall only if it's a Yandex bot.
I do the same thing with Google, I block the entire Google range and open holes in the firewall just for the stuff I want so a ton of stuff from their ranges goes bouncing off my servers on a regular basis.
I wouldn't have to do that if the crawlers wouldn't mix the usage of their IPs and/or properly label the user agents for other IP activities or set the rDNS, but they don't so BLOCK.