In the knowledge Base you may have categories where its articles are only shown to a specific group of users. In some case, in the Service Portal these categories are visible to all users even if they do not have access to the articles within them.

All Supported

There is an widget Instance Option called "Max number of articles evaluated per category to determine visibility" which defaults to 0. When this is set to 0, all the categories will show up even if the users do not have access to the articles within them. To change the behavior, set this number to 1 or higher. ! means that the user must have access to at least 1 article in the category for the category to be displayed. 

1. As an Admin, navigate to the Knowledge Categories page in the portal. https://instance_name.service-now.com/sp?id=kb_category
2. With your cursor, hover over the Categories, press down the Control key and click at the same time. This will open a menu.
3. Select Instance Options
4. Locate field "Max number of articles evaluated per category to determine visibility" and set that to 1.