WARNING: don't use subdomains if you want users in China to be able to get to your site. By default, most/all subdomains managed like this do not get put in China's DNS properly. Get used to life with the great firewall, it is what it is ;)
http://www.apnic.net/apnic-bin/ipv4-by-country.pl?country=CN
I wrote a script a while back that parses that list and creates an access-list for country blocking. Maybe I'll put it online one day.
At least that's how us network folk do it.
And if you think only spamming happens from China, you haven't compared the current account balances of the U.S. and China lately ;).
The subdomains problem seems to do more with DNS replication and pessimistic acceptance of DNS records more so than a person actually censoring content.