Walrus,
I'm not 100% sure on this since I just started using wordpress myself. In the admin area under options/discussion, you can hold a comment in the queue if it contains more than "?" links. When ? is a value you set. There are other options you can set there to slow down or stop the spamming. You can also check the wordpress codex for more information.
http://codex.wordpress.org/Working_w...g_Comment_Spam