Comment and trackback spam began propagating through the web in 2003 and they haven’t stopped spreading since. Jay Allen created one of the original comment anti-spam tools which worked by allowing users to keep a blacklist and disallow comments from known spammers.
It’s been five years, and the tools for combating comment spam have evolved. Instead of relying on a blacklist as in the days of yore, newer anti-spam services use a variety of tests and heuristics to decide what category a comment falls in.
Comments are classified either as “ham” (a valid comment), “spam” (a bad comment), or “unknown” (unsure). Generally, the ham comments are allowed to go straight through, spam comments are blocked, and unknown comments are held for moderation.
Instead of being built into publishing platforms such as WordPress or Movable Type, most anti-spam solutions are run as web services. The publishing platform will either come with an anti-spam plugin or have some available that will talk to the remote web service to determine the status of a comment.
Here I present three of the best anti-spam tools currently available.
Akismet
Akismet has long been the best anti-spam tool available for use with WordPress. Akismet is free for personal use, but for commercial use a license is required. Akismet is most commonly used as a WordPress plugin, but it is available for other platforms including Movable Type, Drupal, phpBB, Joomla, and more. Libraries have been developed that enable its use in Java, .NET, PHP, Python, Ruby, and more.
Mollom
Mollom is new to the anti-spam game and is is currently in public beta. It originated as a module for the Drupal content management system. It combines many of the techniques discussed above, but to ease the process of moderation also incorporates a CAPTCHA on “unsure” comments to test if the comment is coming from a human rather than a spam bot.
A Mollom plugin for WordPress — WP Mollom — is under development by Matthias Vandermaesen.
Mollom libraries have also been developed for Java, Ruby, Python, .NET, and PHP.
Final pricing for Mollom hasn’t been determined, but according to the pricing page, “The basic Mollom service will be free — yes, as in beer — but it will be limited in volume and features.”
TypePad AntiSpam
TypePad AntiSpam became the newest player in the fight against spam when it was released today (5/29/2008). Six Apart has been doing testing of the service for a few months and today declared it ready for open beta.
Having glowing words from TechCrunch won’t hurt early adoption of the service, and you can’t beat the price. “TypePad AntiSpam beta is free for any type of use, personal and commercial, regardless of how many comments you receive.”
Coming out of the gate, TypePad AntiSpam has plugins for Movable Type 3 & 4 and WordPress 2.5. Six Apart is encouraging developers to get involved and create libraries for languages and plugins for other platforms.
Coming to Conclusions
Up until now, I have been using Akismet to protect my sites from spam. However, I have decided to try TypePad AntiSpam based on the price, compatibility with the Akismet API, and because it has been released as open source. Thus far, I have had no problems.
If you’re looking for the most established solutions, at this point Akismet has been around longer, isn’t a beta product, and has a reputation for stopping comment spam. As Mollom and TypePad AntiSpam mature, they will garner more attention and usage throughout the web.