WordPress has excellent support for SPAM fighting. I was satisfied with the default functionality so far. The only thing I did was setting up pre-moderation of comments that match the list of words.
No SPAM comments were posted on the site since I migrated to WordPress and that says something. I can still remember the pain I had while using Nucleus CMS. At those times all comments were posted straigh away and I had to go find and delete them manually. That was very time consuming and error prone procedure that resulted in a lot of swear words and lost comments.
Anyway, with time I became confident of WordPress filtering and now I think that I am spending too much time pre-moderating comments. Most of them are very obviously SPAM and should be killed upon arrival automatically. Thus, I have used the bigger part of the list mentioned above to filter comments that should be blacklist. That is I won’t even see that the comment was posted if it matches one or more of the words.
Another problem that was annoying me recently is referer SPAM. I am checking the list of refering sites on a daily basis and all those SPAM links break my concentration. To solve this problem I installed the AutoBanReferer plugin.
With all these changes there is a chance that something will go wrong. Either I will be missing comments, or pages won’t be displayed, or I won’t be visiting back to your websites. Nothing in this list scares me as long as you can always Contact Me and let me know that you noticed something malfunctioning.