Our blog hosting comes with several spam filters installed, which should protect all blogs from most forms of comment and forum spam. However, if you notice a large amount of spam within your blog, please check your spam settings within your admin section, as well as your signup and comment settings. You should only allow registered members to be able to comment on your blog posts. Also, make sure the captcha feature is working to stop automated signups.
If, after taking all precautions, you still notice a lot of spam sneaking through, please do let us know so we can look into it.