I have made a few small changes to JSSpamBlock, my WordPress spam detection plugin. I found that the plugin had some problems with custom WordPress themes, since some theme developers apparently don’t include the comment form hook. I have added instructions on how to call JSSpamBlock manually from the template file. I have also fixed the plugin for older versions of WordPress which did not have the wp_die() function.

The plugin is now hosted at the WordPress Plugin Directory. You can find it’s page here: JSSpamBlock 1.2. If you have a working installation, there is no reason to upgrade.

I got my first comment spam on this blog the other day. It inspired me to try an idea I got a few months back. My theory was that these bots aren’t very smart – they are programmed to post as many comments as possible on as many sites as possible, hoping that a handful of these comments would get past whatever system the blogger was using to prevent spam. I hypothesized that these bots did not understand JavaScript, and that by requiring some JavaScript to run in the browser I would be able to check with reasonable accuracy weather the comment was submitted by a human or a bot.

I wrote up a simple plugin to test the theory. I checked the logs to find that I was right. In fact, most of the bots that were spamming my blog did not even include the hidden element, which indicates that they were posting to the wp-comments-post.php file directly rather than accessing the form first. The bots that did access the form did not execute the JavaScript and therefore their comments were blocked. Since the trick only involves JavaScript, most users will not even notice the difference. Users without JavaScript simply need to follow the given instructions to copy a number to a text box in order to prove they are human. This is what users without JavaScript will see:

JSSpamBlock Screenshot

If you want to use JSSpamBlock on your blog, check out the JSSpamBlock project page.