Sudden deluge of spam comments???????

Starting this week, my blog is getting spammed like crazy with random commentators spamming me with multiple random hyperlinks. They automatically go to moderation where I can kill them, but it’s getting worse every day. I had two a few days ago, three or four yesterday, and now six today. It’s getting worse every day…

Can I incorporate that thingy that requires commentors to re-write in the letters or answer stupid question just to verify that they are human and not spam bots when they try to leave comments?