Is it actually affecting the performance of your website? If it's just an annoyance in the logs, install fail2ban and configure it so that after X bad requests the IP is automatically banned. Soon you'll have a number of IP's banned and blocked.
If it's actually affecting your bandwidth talk to your provider about blocking out particular sites. You need to decide if it's worth blocking regions or just trying to limit certain kinds of requests; assuming you have a business account (which you should for hosting) they will need to block it farther upstream in order to prevent your connection from getting overwhelmed.
You can also google for methods of automating firewall rules to block sites, but that won't help your bandwidth if that's an issue, since the requests still make it to your server.
I'd suggest you make sure you triple check that the latest updates are in place for Wordpress. It's like a magnet for hacks.