poku

“Block Spam Comment” definitely blocks comments of bots without settings or Captcha.
The three systems of “Block Spam Comment” using JavaScript make it impossible for bots to post comments, because bots cannot use JavaScript. Spam comments are not saved, so it reduces load on your server and save time to delete spam comments.
You can see how many spam comments were blocked and data about IP and user agent of bots. You also can download the csv file with that data.

Block Spam Comment

Block spam comments definitely without settings or Captcha.

OneOfOne

This plugin plugin blocks spam in comments automatically, without requiring any end-user input or any javascript.
<ul>
<li>As of version 0.7.7 there’s an option to add an extra javascript check, it’s off by default.</li>
</ul>
In a way it’s similar to webvitaly’s <a href="https://wordpress.org/plugins/anti-spam/" rel="ugc">Anti-Spam</a> however this doesn’t require the user to enter anything at all.
The comment gets marked as spam if any of the following rules are true :
<ul>
<li>If the comment is a trackback.</li>
<li>If the time between loading the page and commenting is less than 10 seconds.</li>
<li>If the Session variable specific to this form is not set.</li>
<li>If the hidden input field have a different value than “-“.</li>
<li>If the comment includes more than 3 urls.</li>
<li>If the referer isn’t set properly.</li>
</ul>
Once the comment gets flagged as spam, and if the auto delete option isn’t set, a json string will be appended to it to show why it was marked, for example :
<pre><code>{ "is-trackback": 0, "no-session-token": 0, "hidden-field": 1, "number-of-urls": 5, "referer": 0, "too-fast": 1.902538061142 } </code></pre>
Translates to :
<ol>
<li>They changed the hidden input field.</li>
<li>They Had 5 URLs in the comment.</li>
<li>It Took 1.9 seconds to submit the comment since the page was loaded.</li>
</ol>
Also note that the time calculations are per-form, so there are no false-positives if the user has multiple pages open on the site and commented on 2 of them in a short period of time.
Feel free to fork it and submit patches / fixes on <a href="https://github.com/OneOfOne/ooo-nospam" rel="nofollow ugc">github</a>

OneOfOne’s NoSpam

Extremely simple, 0 configuration and 0 user/admin-interaction anti-spam plugin.

Block Spam Comment vs OneOfOne’s NoSpam