There are thousands of anti-spam plugins but you don’t want them all. Most will slow down your blog and as a matter of fact, I tried over 50 variations of spam plugins; some caused error and some did not work.
Akismet- Akismet filters out your comment and track-back spam. It is installed on all wordpress by default so all you need is the API key. If you are in individual running a personal blog then you can get this for free. Business blogs will have to pay a small monthly fee and it’s worth it. So get the Akismet API key and activate Akismet on your wordpress blog.