Yoshimura Hiroyuki

This Plugin blocks comments which is judged to be ‘spam’ by a standard WordPress function. When a ‘spam’ comment is submitted, an error message is shown and the comment will not registerd.
このプラグインは、WordPress標準のコメントブラックリストによる判定の結果’spam’となったコメントを、登録させないで、エラー画面を表示する。
つまり、スパムコメントが溜まりません。
<h3>Arbitrary section 1</h3>

Spam Blocker S1

This Plugin blocks comments which is judged to be 'spam' by a standard WordPress function.

Samir Shah

This plugin has two modes – basic and Akismet-enhanced.
Basic mode: the plugin will serve a CAPTCHA to all commenters that aren’t logged in and don’t have a previously approved comment. Repeat commenters will never see a CAPTCHA.
Akismet-enhanced mode (recommended): the plugin will serve a CAPTCHA only if Akismet identifies a comment as spam (much less frequently than the basic mode). Just install an activate <a href="https://wordpress.org/extend/plugins/akismet/" rel="ugc">Akismet</a> to enable this mode.
Note that a CAPTCHA will only appear after a comment is submitted. When a commenter is served a CAPTCHA:
<ul>
<li>If they fail, then the comment will be automatically discarded or trashed (and won’t clutter up your spam queue).</li>
<li>If they pass, it will be allowed into the spam queue (or approved, if you so choose). This means that any false positives from Akismet will be easily identified without you having to trawl through all the spam comments manually.</li>
</ul>
Most genuine commenters will be able to comment on your site hassle-free, without ever seeing a CAPTCHA.
The default CAPTCHA is a simple text-based test. There is also the option to use <a href="http://www.google.com/recaptcha" rel="nofollow ugc">reCAPTCHA</a> if you want something more robust (free API key required). You can also style the CAPTCHA page to fit with your own WordPress theme.
If you come across any bugs or have suggestions, please use the plugin support forum or <a href="http://rayofsolaris.net/contact/" rel="nofollow ugc">email me</a>. I can’t fix it if I don’t know it’s broken! Please check the <a href="https://wordpress.org/extend/plugins/wp-conditional-captcha/faq/" rel="ugc">FAQs</a> for common issues.
Thanks to the following people for contributing translations of this plugin: Belorussian – <a href="http://pc.de" rel="nofollow ugc">Marcis G</a>, Brazilian Portuguese – Stefano, Czech – <a href="http://trumplin.com/" rel="nofollow ugc">Ted</a>, Danish – Jesper, Dutch – <a href="http://wpwebshop.com/books/" rel="nofollow ugc">Rene</a>, Estonian – <a href="http://www.itransition.com" rel="nofollow ugc">Itransition</a>, Finnish – Jani, French – <a href="http://android-software.fr" rel="nofollow ugc">Laurent</a>, German – <a href="http://jochenpreusche.com" rel="nofollow ugc">Jochen</a>, Hindi – <a href="http://outshinesolutions.com" rel="nofollow ugc">Outshine Solutions</a>, Hungarian – <a href="http://www.televizio.sk" rel="nofollow ugc">Gyula</a>, Italian – <a href="http://gidibao.net" rel="nofollow ugc">Gianni</a>, Lithuanian – Mantas, Polish – <a href="http://www.spin.siedlce.pl" rel="nofollow ugc">Pawel</a>, Romanian – <a href="http://simplu.mixnet.ro" rel="nofollow ugc">Lotus</a>, Russian – <a href="http://www.everycloudtech.com/" rel="nofollow ugc">Ivanka</a>, Spanish – <a href="http://www.reinventia.net" rel="nofollow ugc">Reinventia</a>, Swedish – <a href="http://www.umu.se" rel="nofollow ugc">Hugo</a>, Turkish – Tony, Ukranian – <a href="http://www.everycloudtech.com/" rel="nofollow ugc">Ivanka</a>. Some of these translations are a bit out of date – updates welcome!

Conditional CAPTCHA

Asks commenters to complete a simple CAPTCHA if they don't have a previously approved comment, or if Akismet thinks their comment is spam.

Spam Blocker S1 vs Conditional CAPTCHA