BlogEngine.NET comment spam filtering

It’s been a month or three since I was utterly fed up with comment spam on my blog. Sure, I did turn on comment moderation so you, as a visitor, would not notice this spam if I did not approve it as a valid comment. However, I found myself cleaning up comment spam from in between legitimate comments in the BlogEngine.NET admin interface.

In an effort of trying to reduce comment spam, I tried the following:

• Close comments after 90 days – This effort worked for a few days, but afterwards I was just seeing more comment spam on the topics that were still open to comments.
• Use a CAPTCHA – This effort reduced some comment spam, but not all. Which makes me believe there are people actually making a living by just sending out comment spam and filling out CAPTCHA’s out there.
• Whining and cursing while again cleaning out comments manually – This effort worked, until I found out that this was what I’ve been doing before the other 2 efforts. Back to start…

Luckily, the latest version of BlogEngine.NET (and also earlier version if you go down the hacky road) featured a new comment system, including spam filtering. After using it for a few months, I must say I’m very close to zero comment spam!

The results

I have configured BlogEngine.NET as follows:

• Comments enabled, never closed
• Comment moderation: “on” and “automatic”
• Whitelisting rules enabled (if you have 5 legitimate comments, you are probably OK)
• Spam filters enabled: AkismetFilter, StopForumSpam and TypePadFilter

Now if you look at the results, there’s an interesting difference between the spam filter services being used:

The accuracy of the spam filters is mostly > 90%, for Akismet it’s even 97.30 %. Which I also feel: a small check every week on whether there are spam filter mistakes is quite enough. Only the TypePadFilter is letting me down there, and I will probably disable this one and rely on only two filters.

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