BlogEngine.NET, SimpleCaptcha, and Spam

I use BlogEngine.NET for this blog. I've loved it so far. It suits me perfectly because I also love .NET and C#.

BlogEngine.NET comes with a few "extensions" out of the box, and one of those extensions is called SimpleCaptcha. You simply configure it with a question and an answer. Visitors who supply the correct answer get to post comments. This wards off most of the spammers. But from what I'm seeing, is that whatever spammers use to automatically crawl the web, leaving little spam-filled coprolites in their wake, seems to be able to solve simple mathematical equations like 5+5, 3+7, and even (5+2)-1. I changed my captcha challenge to that latter equation and received a spam comment not five seconds later.

Maybe this will stop them...

So I figured the next best thing to do, without annoying and frustrating my visitors too much with those really bizarre graphical captchas that you can't even read half the time, was to change my SimpleCaptcha to something that was still simple, but required slightly more human-like thinking than what I suspect most spambots are capable of. Questions such as "what is the opposite of cold" or "a shape with four equal sides." These sorts of questions have brought my comment spam to a screeching halt. But there's one last problem: SimpleCaptcha is case sensitive and there's no immediately apparent way to turn it off. I don't want a visitor to type "Square" and not get their comment posted because they needed to have typed "square" instead.

So, to remedy this problem, simply access your web server and browse to wherever you have IIS/BlogEngine.NET installed. Then drill down to where SimpleCaptcha is. For me, it's C:\inetpub\wwwroot\App_Code\Extensions\SimpleCaptcha\. Open up the file SimpleCaptchaControl.cs in a text editor (or Visual Studio if you'd rather,) and find this method:

public void Validate(string simpleCaptchaChallenge)
{
   this.valid = this.skipSimpleCaptcha || this.simpleCaptchaAnswer.Equals(simpleCaptchaChallenge);
}

Simply change that one line to this:

public void Validate(string simpleCaptchaChallenge)
{
   this.valid = this.skipSimpleCaptcha || this.simpleCaptchaAnswer.Equals(simpleCaptchaChallenge,StringComparison.OrdinalIgnoreCase);
}

And you've just made your SimpleCaptcha not case-sensitive. The change takes effect as soon as you save the file; no restarts of anything are required.