Thread:Project:Support desk/Easy way to implement massive IP range blocks?

I'm running a very small wiki. I'm having some problems with spammers. I have a hosting package with another company which may limit to some degree what I'm capable of doing. Geolocation tools say that the spammers are virtually all coming from a specific part of China, but the "real" users of the wiki are only from a specific bit of Southern California, so I'd kind of like to block write permission (or block account creation) for all of the world except for the US. Apparently, this would mean a set of IP range blocks something like the following: 217.0.0.0/8 218.0.0.0/7 220.0.0.0/6 224.0.0.0/3 but the Mediawiki interface will only let me do /16 IP range bans, which would be an incredible amount of range bans. Any suggestions on how to stop these spammers from creating user accounts without mandating that every "good" user account be individually vetted and allowed to come on board?