Starting in 1976 he has been on the MIT EECS department faculty, at Xerox PARC, and at the DEC Systems Research Center.
At MIT he was involved with Multics, where his contributions included a seminal work on security architecture for shared information systems.
[3] In 2006, ACM SIGSAC presented him with the Outstanding Innovations Award "for technical contributions to the field of computer and communication security that have had lasting impact in furthering or understanding the theory and/or development of commercial systems."
He is a leading expert on the American landscape painter Gilbert Munger (1837–1903), for whom he authors a web-based catalogue raisonné and archive of period documents.
Gray Sweeney of Arizona State University he wrote the book Gilbert Munger: Quest for Distinction (Afton Historical Society Press, 2003).