Someone at 200.141.76.227 has been giving me nasty rape trackback spam all evening. I'd block it, if I were you.
Update: You can also ban 207.8.131.172 and 198.26.123.36 (thanks Richy) or see Richy's trackback for a whole list of anonymous proxies/zombified computers which may be used for comment/trackback spam.

I’ve just had the same myself - 198.26.123.36.
I’m just blocking both IP addresses using Cpanel’s IP Deny functionality BTW
Thanks guys, I’ve just blocked both to be on the safe side.
I have banned them as well.
You better add 198.26.120.13 as well - another 30+ trackback spams just hit me from there. I’ve just actually blocked that whole netblock now (198.25.0.0-198.26.255.255) as it all belongs to the same organisation (a certain ‘security/defense’ organisation in the states with a building with 5 sides!)
Yeah I had exactly the same trackback spam (45) from 12.150.236.154
hi there.. just happened to drop by here.. u have any idea how to block a IP address from ur blog? i using blogspot..