Blogger users I think know about this by now, but just in case not…
To make life harder for the comment spammers, Blogger have introduced a word verification option (explained in that link).
Best to turn it on, if you haven't already, by ticking Yes against "Show word verification for comments?" in your Settings for Comments. More hassle for legit commenters, I know, but it should stop automated comment spam (though to be honest I get more trackback spam than comment spam, myself).
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