Blog spam flood

I have been flooded with blog comment spam, perhaps the most pernicious problem affecting blogs hosted by Blogspot. The spammers use software that searches for keywords and generates some text that directs people to a website. I had a post about hardware and I got this spam:

Found a lot of useful info on your site about soldering - thank you. Haven't finished reading it yet but have bookmarked it so I don't lose it. I've just started a soldering blog myself if you'd like to stop by

What is a soldering blog? Does it give advice about how to solder properly? Anyway, I finally got tired of deleting spam, so I have implemented the word recognition feature for comments.