Blocking Spam

As your site becomes better known, it is virtually inevitable that will become a target for spam (online junk mail). One of your best defenses against spam is Mollom, which is easy to install and in most cases free to use.

We highly recommend adding Mollom to any site that includes the ability for anonymous users to post content, complete online forms or add comments. On many sites we have seen the number of successful spam attacks go  from hundreds of bogus posts per day to zero.

What is Mollom?

Mollom is an "intelligent" content moderation web service. By monitoring content activity on all sites in the Mollom network, Mollom is in a unique position to determine if a post is potentially spam; not only based on the posted content, but also on the past activity and reputation of the poster. In short, Mollom handles incoming posts intelligently, in much the same way a human moderator decides what posts are acceptable. Therefore, Mollom enables you to allow anonymous users to post comments and other content on your site. Mollom is co-founded and directed by Dries Buytaert, the founder lead developer of the Drupal project.

How Mollom works

Mollom may block a post outright if it is from a known spammer. If Mollom is unsure how to classify a post, it may require the completion of a CAPTCHA to accept the post. Posts that do not match a "spammy" text pattern and do not originate from known spammers are accepted without the need to complete a CAPTCHA. Essentially, Mollom acts as a proactive content moderator that is on the job 24 hours a day, 7 days a week.

A stand-alone CAPTCHA solution, which neither considers user behavior nor point of origin, can never achieve this level of informed protection, and generally requires users to solve a CAPTCHA on every post. Using Mollom's text analysis, users must only solve CAPTCHAs when Mollom is unsure about a post.

The Mollom module allows other modules to integrate their forms with Mollom. Forms exposed by Drupal core, including the user registration and comment forms, are supported by default.

Mollom is actively developed and maintained by Dries Buytaert, the founder and project lead of Drupal, and Benjamin SchrauwenMollom is currently used by more than 30,000 sites, including Sony, Adobe, LinuxJournal, Warner Bros Records, Netlog, NBC, and others. As of September, 2010, Mollom currently protects over 30,000 websites with an average efficiency rate of 99.93% - which means that only 7 in 10,000 spam messages are not routinely caught by Mollom's filters. Since Mollom began operating, it has prevented almost 300 million spam posts from littering the web.

Mollom learns from its mistakes!

If an inappropriate posting slipped through, make sure to report it.  Your Mollom plugin allows you to report mistakes from within your site so it should be a breeze.  Mollom uses feedback to help prevent future mistakes. 

If you want Mollom to become better at blocking spam on your site, it is important to give accurate feedback.  Mollom combines feedback from all participating sites to help make its spam filters better.  Mollom will get better as the install base grows and more people report mistakes.

Increased protection with the paid version

Mollom has built a world-class (and world-wide) infrastructure that evaluates your site's comments and posts in real time, freeing you from moderation duties to spend your time on more satisfying pursuits.

While most sites take advantage of their excellent free filtering service, larger sites often purchase a commercial subscription.  Paying customers gain access to Mollom's high-availability infrastructure, which includes fail-over servers in different data centers around the world. Mollom guarantees paying customers 99.9% availability and low-latency (delays that may slow down your website).  For other differences between Mollom Free and Mollom Plus, see

Companies that use the high-availability infrastructure include Sony Music, NBC, The Economist, Warner Bros, Adobe, Netlog, as well as some smaller business, non-profit organizations and high-profile bloggers.  An incomplete list of their customers is available at

Mollom's service guarantees are in writing at and are part of the service agreement at

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