Blog spam is a phenomenon that seems never ending and it's a terrible noise to see that, despite the remedy that everyone of us now has adopted, sometimes some spam's posts avoid all the walls and enters on your blog's engine. For example, actually spam comments don't place their words and links only on the text of a post but also on the author and the URL field and if you've not the right countermeasure you will be full of masked spam. 
I've to admit that I was too lazy (and busy) to find a new solution and I my actual blog's antispam remedy was the CAPTCHA and a trigger on my database. However, today my blog was under a big spam attack (about 60 spam posts with links masked on the author and url fields) and so this evening my decision was to absolutely update my trigger to check for spam also on all the parts of a blog's post record.
Now I've a completely new solution that seems to work good. 
I don't want to publish here the solution (and I think that you can understand what are the reasons 
), but if someone (as in the past) is interested on it, just contact me and I'll share with you.