Mod_authz_unixgroup is a unix group access control module for apache 2.1 and later. if you are having users authenticate with real unix login id over the net, using something like my mod_authnz_external / pwauth combination, and you want to do access control based on unix group membership, then mod_authz_unixgroup is exactly what you need.

this package includes the mod-authn-unixgroup module for apache version 2.4