AbuseFilter is a MediaWiki extension used to detect likely abusive behavior patterns, like pattern vandalism and spam. In 2013, Global AbuseFilters were enabled on a limited set of wikis including Meta-Wiki, MediaWiki.org, Wikispecies and (in early 2014) all the "small wikis". Recently, global abuse filters were enabled on "medium sized wikis" as well. These filters are currently managed by stewards on Meta-Wiki and have shown to be very effective in preventing mass spam attacks across Wikimedia projects. However, there is currently no policy on how the global AbuseFilters will be managed although there are proposals. There is an ongoing request for comment on policy governing the use of the global AbuseFilters. In the meantime, specific wikis can opt out of using the global AbuseFilter. These wikis can simply add a request to this list on Meta-Wiki. More details can be found on this page at Meta-Wiki. If you have any questions, feel free to ask on m:Talk:Global AbuseFilter.