WordPress.org

Author: Peter van der Does

The AVH First Defense Against Spam plugin gives you the ability to block spammers before any content is served. Spammers are identified by checking if the visitors IP exists in a database served by stopforumspam.com, the Project Honey Pot or a local blacklist.

Features

• The visitor's IP can be checked at the following third parties:
  • Stop Forum Spam. http://www.stopforumspam.com
  • Project Honey Pot. http://www.projecthoneypot.org (An API key is needed to check the IP at this party. The key is free.)
• Spammers can be blocked based on the information supplied by the third party or by using a local blacklist.
• Separate thresholds can be set for the following features:
  • Send an email to the board administrator with information supplied by the third party about the spammer.
  • Block the spammer before content is served.
• Bypass the checks for the IP at the third parties and the local blacklist, based on IP in the local whitelist.
• Ability to add single IP's and/or IP ranges to the blacklist and whitelist.
• When an IP is blocked a message can be displayed to the visitor with the reason why access was blocked.
• Report a spammer to Stop Forum Spam. A valid API key from Stop Forum Spam is necessary.
• Add a spammer to the local blacklist by clicking a link in the received email.
• Block spammers that access wp-comments-post.php directly by using a comment security check. An email can be send when the check fails.
• IP Caching system.
• Use a honey pot from Project Honey Pot

Blocking a potential spammer before content is served has the following advantages:

1. It saves bandwidth.
2. It saves CPU cycles. The spammer is actually checked and blocked before WordPress starts building the page.
3. If you keep track of how many visitors your site has, either by using Google's Analytics, WP-Stats or any other one, it will give you a cleaner statistic of visits your site receives.

The IP Caching system.

Stop Forum spam has set a limit on the amount of API calls you can make a day, currently it iset at 5000 calls a day. This means that if you don't use the Blacklist and/or Whitelist you are limited to 5000 visits/day on your site. To overcome this possible problem I wrote an IP caching system. If you use the caching system you still have a limit with Stop Forum Spam , but the limit is set to 5000 unique visits/day.

The following IP's are cached locally:

1. Every IP identified as spam and triggering the terminate-the-connection threshold.
2. Every clean IP.

Only returning IP's that were previously identified as spammer and who's connection was terminated will update their last seen date in the caching system. Every day, once a day, a routine runs to remove the IP's who's last seen date is X amount of days older than the date the routine runs. You can set the days in the adminstration section of the plugin. You can check the statistics to see how many IP's are in the database. If you have a busy site, with a lot of unique visitors, you might have to play with the "Days to keep in cache" setting to keep the size under control.

Checking Order and Actions

The plugin checks the visiting IP in the following order, only if that feature is enabled of course.

1. Whitelist - If found skip the rest of the checks.
2. Blacklist - If found terminate the connection.
3. IP Caching - If found and spam terminate connection, if found and clean skip the rest of the checks.
4. 3rd Parties - If found determine action based on result.

To my knowledge this plugin is fully compatible with other anti-spam plugins, I have tested it with WP-Spamfree and Akismet.