Akismet

 Akismet  is an anti-spam webservice from Automattic that has various levels of service both free and paid. Comments can be submitted via their API and the service will respond with "true" if the comment is spam, or "false" if it is not. The service is free for non-commercial sites.

IndieWeb Examples

 * Amanda Maclean uses a ProcessWire module.


 * used a modified Nucleus plugin on gregorlove.com until 2015-07-12 when I switched to ProcessWire. As of 2016-03-21, I support local comments again with a combination of a honeypot and Akismet.
 * Spam statistics: https://gregorlove.com/2017/03/spam-statistics-since-2017-05-10-when/

Libraries

 * gRegorLove/php-akismet - simple PHP class for interacting with the Akismet API

Supported Platforms

 * There are Akismet plugins for a variety of systems, including WordPress, Drupal, MediaWiki, and Joomla. https://akismet.com/development/
 * Known has a community plugin that supports Akismet as well.

API
There is an API that handles checking comments for spam, submitting spam comments, and submitting ham comments. https://akismet.com/development/api/

Issues

 * In March 2011, a lot of spam was getting past Akismet on many of 's sites for several days. Upon contacting support, the response was "we're not seeing any signs of missed spam." The problem was intermittent over the next several days, with another resurgence. Again the response from support was "none of your sites are reporting any missed spam or wrongly caught comments".
 * As of September 2012:
 * Akismet only returns a 'true' or 'false' value for whether something is Spam. Many other vendors return probability scores as well as other classification labels indicating what 'type' of spam the content is.
 * Akismet could process ~200 comments per minute (not an issue, but worth knowing)
 * Reliability: Akismet showed no failures during testing; all requests completed successfully. However, Akismet does not report errors in passed parameters, and instead apparently simply ignores them. That resulted in lower accuracy during the first batch of testing, and we didn't learn about it until a contact within the company has manually reported the errors.


 * Ships by default with Wordpress (but is not activated, API key has to be requested manually(?)), but does not inform the user about it's use (as legally required in some jurisdictions). Additional plugins exist to handle this, assuming the site operator is aware of it.

Alternatives
Antispam Bee does not send any user information by default (some features require external handling, with adequate privacy warnings in the settings) to third parties and is hence an alternative protecting users' privacy.