Lately I am getting lots of spam comments to my blog entries, mainly concerned with pornographic sites or anti-impotence drugs sale. This is really annoying, and although my comments are not published automatically, but are rather stored in approval queue, it wastes more and more of my time to go through it and delete all of them.
A valid option would be to use a captcha module for Drupal. I tried it, but it obviously has some bugs, which prevents even humans from posting, so it is not really useful.
I am considering the deployment of the spam module for Drupal - if it reduces the amount of garbage I'm getting then the current arrangements can be kept as they are.
Another option, recommended on the Internet is to block some sites via .htaccess file in Apache. While quite interesting and practical short-term solution, that would require a lot of manual maintenance.