Trackback spam is something you'll deal with using any blogware.
There are Wordpress plugins that can help you deal with it. See <a href="http://www.wp-plugins.net/">The WP PluginDatabase</a> for all the amazing plugins people have built for WP.
Incidentally, I've noticed that with WP 1.5 my comment spam is down to nearly zero. They've done good work with comment spam. Trackback spam is yet to get worked on.