<p>Lately I&#8217;ve been spammed a lot in this blog, so I decided I had to implement some kind of captcha, a way of checking if it is a real person submitting that form. <a href="http://www.tonsai.de/blog-english/2007/craziest-captchas-on-the-web/">Here you can check some wicked examples</a>. Through <a href="http://sergiosantos.info/">S&#233;rgio</a> I learned about reCaptcha, a project that uses captchas to complement <span class="caps">OCR</span> programs. You can read more about this in his <a href="http://sergiosantos.info/2007/5/recaptcha">post</a>.</p>

<p>I was having some issues trying to implement it, when <a href="http://twitter.com/BrunoFigueiredo">Bruno Figueiredo</a> told me about Negative Captchas. I googled it and I found out that was a pretty nice system. I added a &lt;input name=&quot;email&quot; value=&quot;&quot; /&gt; hidden with <span class="caps">CSS</span> and changed the email field to &#8220;email_alt&#8221;. Bots fill all the fields for default, so if the email field has some content, it was a bot since users can&#8217;t see it. Easy and users won&#8217;t notice.</p>

<p>However, the <b>negative captcha</b> technique has a downside: Spammers can make custom bots to spam the system, but since this is a not-so-popular weblog I&#8217;ll take that chance.</p>

<p>Oh and a small time-waster:</p>

<embed src="http://www.collegehumor.com/moogaloop/moogaloop.swf?clip_id=1771556" quality="best" width="400" height="300" type="application/x-shockwave-flash"></embed>