Who Let The Bots Out? – Elf Knows It [ARCHIVED]

I came back to my blog today to find I had been attacked by a gang of spam bots!, Opening blog comments to guests always poses this threat!, So I have had to add a simple image verification to comments, and the contact form, Nothing major, Just 5 simple letters to re-type! I figured this is the better option rather than blocking comments to guests!

How do you tackle the spam bots?