By default, the access setting when creating a new shared link will be "Invited People Only", meaning only people who have been invited to the item (folder or file) can access the content. This is the most secure setting and ensures that only invited users have access.
This setting can be changed to "People in your Company" or to "People with the link (public/open)" depending on your access needs. Instructions for how to change this are at http://support.box.com.
IMSS encourages you to check the settings of your existing shared links and verify that the sharing is set at the needed security level.