First spam appearing in one of my Drupal sites

Today I noticed a few posts on a forum of one of my Drupal sites. Nothing serious, just a spammer putting tons of links on my site. Since my site does not have a really good rank (it's just a personal page!) and the page included a good hundred links, there is no way it would have been useful in regard to search engines since they discard those immediately.

Why did it happen? I actually installed a forum where anonymous users could post. Oops 8-) Of course, this was an easy fix. Now the users won't be able to publish their posts. Since I don't really get any anyway, it won't matter much (at least for some time.)

The following is a sample of the page (which is done now.) As you can notice, there is no way to read anything (well.. it would be hard work.)