John Dalesandro

The Analytical Spam Filter plugin for WordPress blocks comment, trackback, and pingback spam. It uses multiple spam detection methods without challenging the user with obstacles such as captchas, math problems, etc. and it does not rely on external services or APIs. This is a low overhead plugin that begins blocking spam as soon as it is activated. It is compatible with caching plugins as long as the user has JavaScript enabled. The plugin blocks spam submitted through the default WordPress comment form only.
Logic is used to identify spam comment submissions. No user interaction is required. The spam blocking mechanisms work transparently behind the scenes. Most visitors will require longer than a few seconds to read a post and add a meaningful comment so any comments submitted within a short time threshold are identified as spam. Comments containing a large number of links are flagged as spam. The plugin uses an encrypted code and a honeypot to filter robotic submissions. All field names added by the plugin are randomized to prevent detection based on a source code signatures.
Configuration options include:
<ul>
<li>Enable Cache Compatibility (requires JavaScript)</li>
<li>Add spam to WordPress queue or block completely</li>
<li>Send diagnostic information to site administrator</li>
<li>Automatically compatible with the Micro Contact Form plugin to block spam messages.</li>
</ul>
Blocking options include:
<ul>
<li>Honeypot Trap</li>
<li>Randomized Internal Field Names</li>
<li>Timestamps (minimum and maximum entry time)</li>
<li>Aggressively check for excessive URLs</li>
<li>Check if JavaScript is enabled</li>
<li>Automatically block repeated spam from IP</li>
<li>Automatically block repeated spam based on content</li>
<li>Require User Agent string</li>
<li>Require Referer</li>
<li>Block Trackbacks</li>
<li>Block Pingbacks</li>
</ul>

Analytical Spam Filter

Block WordPress comment spam, trackback spam, and pingback spam through intelligent analytics instead of interactive challenge response tests.

Dana Ross

Check comment against the SpamBot Search Tool using the IP address, the email and the name 
of the poster as search criteria. If anyone has already reported the user a as a known 
spammer the plugin will not let the comment to be posted and an email will be set to the 
blog admin. You can use your own installation of SpamBot Search Tool or you can use the 
Xavier Media server.

WP-Check Spammers

Check comment against the SpamBot Search Tool using the IP address, the email and the name of the poster as search criteria.

Analytical Spam Filter vs WP-Check Spammers