You can specify user criteria for an article to control which users can read the
article.
If an article has no user criteria selected, the
article is available to all users, including unauthenticated users, who have access
to that knowledge base (based on the user criteria for the knowledge base).
Knowledge base user criteria restrictions override article-level user criteria. For
example, a knowledge base that is configured to restrict user access overrides any
access granted at the article level.
If a user has contribute access to the knowledge base, article-level user criteria
are not evaluated and the user can read all articles in the knowledge base. If a
user has read access to the knowledge base, article-level user criteria are
evaluated to determine if the user has read access to the article.
On the article level, if Can read user criteria is defined,
only those users specified can read the article. If an article has Cannot
read user criteria defined, those users specified are denied reading
the article. Cannot read user criteria overrides
Can read user criteria for articles.