If you don't need the knowledge base for customers, there is an option to disable the knowledge base functionality.

To deactivate you need to go to Settings->Configuration->Customers and define  Show FAQ section on No.

Staff members #

If you give staff permissions to view the (global) knowledge base, then they will be able to see internal (staff) knowledge base articles in the admin area. 

In this case, to prevent a specific staff member from reading internal knowledge base articles, you should not grant permissions for the (global) knowledge base view.

Keep in mind that if the knowledge base is activated in the customer area, every visitor to the customer area will be able to read the articles.