Best known for co-authoring the Bell-Lapadula Model with David Bell

Wikipedia entry for Bell-LaPadula Model: http://en.wikipedia.org/wiki/Bell%E2%80%93LaPadula_model

Babbage Institute: https://wiki.umn.edu/CBI_ComputerSecurity/PeopleLaPadulaLeonard

Inducted into the (US) National Cyber Security Hall of Fame 2016 http://www.cybersecurityhalloffame.com/

From the Cyber Security Hall of Fame page:

Co-author of the Bell-LaPadula model of computer security

"With a major in Mathematics, Len got his start in computers with IBM in the Time Life building in NYC in 1960. He continued in this new field as an Army Lieutenant with the Army Security Agency Training Center and School at Fort Devens, Massachusetts from 1961 to 1963. There he worked with an IBM 650 (1000 words of main memory!) and taught Fortran programming. After over 40 years with The MITRE Corporation where he worked on numerous federal government contracts, Len retired in 2013.  

"His principal efforts with MITRE supported various initiatives to improve computer and network security, ending with a project on cyber resiliency. In 1973, he co-authored with David Bell a pioneering paper on computer security, which came to be known as the “Bell-LaPadula Model”.  

"This mathematical model became part of the computer science curriculum in many universities, influenced developments in computer systems, and contributed to the “Orange Book” series published by the National Security Agency. As a retiree, he enjoys quiet gardening."