Spam—we all hate it and it’s not just for email anymore, hello Drupal comment spam.

To determine what is effective at preventing Drupal spam, I decided to run a little case study when I redesigned this site and the following are the conclusions I drew from trying a number of different combinations:

1. A Drupal 6 and 7 sites that allows anonymous user comments will be consumed by spam. I was receiving over 500 spam comments a day on this site.
2. Changing the comment settings to force a comment preview for anonymous users reduced spam by 80%, but I was still seeing around 100+ a day.
3. Adding in the captcha module reduced spam even further by about 90%, to only a dozen or so.
4. To catch the remaining spam, I added in the AntiSpam module which was then able to filter out the remaining 98-99% of spam, with only possibly 1 or 2 every few days slipping by.

Of course, if I forced my users to signup and verify their accounts I probably wouldn’t have much of a spam problem to begin with, but why should I put that extra burden on my users?