| Mollom | Akismet | Defensio | |
|---|---|---|---|
| Company | Mollom | Automattic | Websense Inc. |
| When in doubt, use CAPTCHA? | Yes | No | No |
| Protect user registrations | Yes, on some platforms | No | No |
| Supported platforms | Drupal, Joomla!, WordPress, and others | WordPress and others | WordPress and others |
| Multiple language support | Yes | Yes | Yes |
| Commercial partners | Yes | No | Yes |
| Developer API | Yes | Yes | Yes |
| CAPTCHA support | Yes | No | No |
| Reputation tracking | Yes | Unknown | Yes |
| Highly-available back-end network | Yes | Unknown | Yes |
| Ability to retain spam for manual moderation | Yes2 | Yes | Unknown |
| Protection for new user registrations, lost password requests, etc. | Yes2 | Unknown | Unknown |
| Protection for custom and site-wide forms | Yes2 | Unknown | Unknown |
| Hidden honeypots to trap spam bots | Yes2 | Unknown | Unknown |
| Support and feedback | Yes | Yes | Yes |
| Security protocol | HMAC | None | None |
| Free for personal use | Yes1 | Yes | Yes |
| Free for commercial use | Yes1 | No | Yes |