You might think these models are "old school" (Bell-LaPadula was born in 1973). However, modern architectures are a direct evolution of these models.
: Designed for military use to prevent secret information from leaking to lower clearance levels . Information Security Models Pdf
Military systems (e.g., Top Secret, Secret, Confidential, Unclassified). Available PDF Content: Look for the original 1973 paper by David Bell and Leonard LaPadula ("Secure Computer System: Unified Exposition and Multics Interpretation"). Many university CS departments host scanned copies of this historical Information Security Models PDF . You might think these models are "old school"