Preventing access to a SMW site is a frequent use case. MediaWiki itself has some built-in features, see https://www.mediawiki.org/wiki/Manual:Preventing_access, but they are quite limited due to the nature of wikis.
- Semantic Access Control provides group based access control. Access control is defined in template as internal object.
- https://github.com/HaloACL/HaloACL is supposed to revive the Access Control List Extension (HaloACL), due to https://semantic-mediawiki.org/wiki/SMWCon_Fall_2014/Relaunch_of_HaloACL
- https://github.com/mediawiki4intranet/IntraACL http://wiki.4intra.net/IntraACL is another project aiming to revive the Access Control List Extension (HaloACL)