Bell–LaPadula model

The Bell–LaPadula or BLP model is an example of a model where there is no clear distinction between protection and security.

>The model is a formal state transition model of computer security policy that describes a set of access control rules which use security labels on objects and clearances for subjects. Security labels range from the most sensitive (e.g., "Top Secret"), down to the least sensitive (e.g., "Unclassified" or "Public"). page

Also, see - Oral history interview with David Elliott Bell - 2012 page