As given in the documentation here : http://devdocs.magento.com/guides/v2.0/rest/anonymous-api-security.html
By default magento 2 only restrict Catalog, Store and CMS API from anonymous users.
In a same way how I can restrict access for all the available API's in magento 2?
The reason is I am building an Mobile app and website based on Angular and I wanted that only my app and website should have access to all the API.
Best Answer
To disable Anonymous Guest Access Go to
Allow Anonymous Guest Access set to No
Check http://devdocs.magento.com/guides/v2.0/rest/anonymous-api-security.html