According to Email Security Company Postini, IP addresses in the 218.107.x.x class are in the top 10 for both spam and directory harvest attacks. 8 of the top 10 spam sources and 4 of the top 10 DHA sources came from this class for December 31 and January 1. These IP's are registered to China Netcom and have a hostname "host.better-delivery.com". It looks like these ip's may be good candidates to block.
www.postini.com/stats

I hope everyone had a Happy New Year.

Deb