BotBlock with Invisible CAPTCHA

It looks like LinkSleeve has been failing me lately. The past week I've been inundated with comment spam. So, to fix that problem, I updated the BotBlock plugin. You can download version 0.2.0 here. Just unzip and drop it in your LnBlog/plugins directory, overwriting the old version.

For the new version, I basically rewrote the plugin. The old version did nothing but force bots to download the comment form before submitting, which was fairly useless.

The new version, however, implements an invisible CAPTCHA. This is not the annoying image-based CAPTCHA you see all over, but rather a simple math problem. Furthermore, it's "invisible" to anyone with JavaScript enabled - i.e. it includes JavaScript code to automatically solve the CAPTCHA and hide the form field. So, for 90% of visitors, the comment form should work as before, but block any bots that don't interpret JavaScript (which is a lot of them). For the rest, there will be a simple math problem and they will be prompted to type in the answer. (Note: There is an option to turn the non-JavaScript text off, if you're so inclined. Of course, that makes it less accessible, but apparently lots of people are into discriminating against the disabled.)

As a fall-back measure, I also included an option (on by default) for some simple content filtering - that is, comments with HTML links in them get blocked. The idea is that most of the comment spam I get includes plain text, HTML, and BBCode links, but LnBlog only allows plain text in comments. Therefore, anyone who posts a comment with an HTML link is either a spammer or too stupid to read the instructions. Either way, we probably don't care what they have to say.

So there it is. I haven't had any comment spam since installing the new version on my site. Of course, I'm still having problems with TrackBack spam for some reason. Apparently the LinkSleeve and TrackbackValidator plugins aren't working for this particular wave, though I don't know why. I'll have to work on that.

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Comments #

    LinkSleeve and TrackBack spam...

    Hi, I am Russ Jones, the principal programmer for LinkSleeve. Could you email me some examples of spam that got through so we can take a look?


    Will the plugins work woth 1.0

    • Comment posted on Wednesday 14 Sep 2011 at 2:24pm
    • By Aaron

    Re: plugins question

    Yes, they should. There has been no change in the plugin system, so all plugins should still work normally.


    I'll try this out. It looks customizable.

    • Comment posted on Monday 19 Sep 2011 at 7:50am
    • By Aaron

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