I’ve been seeing more and more of the blogs I read lately complaining about comment spam attacks. Having had a bit of experience with this myself, I can sympathize.
The single best thing I can recommend is to get Akismet running on your blog. Since installing it several months ago, I have had zero comment spams. I check my filtered comments pretty regularly, and as far as I can tell, it’s never prevented a real user from commenting, or gotten any false positives. Comment spam has simply stopped being a factor in my life, and it’s nice. Akismet was originally written for WordPress in PHP, but versions have been released for just about everything, including Movable Type and even other platforms and libraries, like Ruby and Perl.
Sadly, the two examples I linked to won’t be able to use this, because Urn rolled his own blog in .NET, and Walkerings is hosted on TypePad (which doesn’t allow plugins, as far as I know).
Askimet is one of the primary reasons I moved my blog from a very-hacked up Blosxom (Perl & flat databases) to WordPress. There were a few growing pains, but the fact that I’ve had absolutely no spam since the transition makes it completely worthwhile.
A point of clarification, though it’s just a tiny, nit-picky thing: my blog is written in ASP, not ASP.NET. You give me more knowledge than I acually have. :)
Though I hate the comment spam, it drives me to continue actually working on my blog. I would like to rewrite the whole thing, to simplify a lot of my code, and make some future redesign easier.