I also have A LOT of this trackback spam shit. especially on one single post, itīs years old. I hate to see that on my stats. I think only 10% of traffic on this project is real, the rest are chinese trackback hits and a lot categorized as "unknown". Itīs really annoying.
I already tried to block lots of IPīs via htaccess, with plugins, but somehow it doesnīt work at all and I gave up
