An abstract of “MULTICS Security Evaluation: Vulnerability Analysis”, one of my favourites!

A security evaluation of Multics for potential use as a two-level (Secret/Top Secret) system in the Air Force Data Services Center (AFDSC) is presented. An overview is provided of the present implementation of the Multics Security controls. The report then details the results of a penetration exercise of Multics on the HIS 645 computer. In addition, preliminary results of a penetration exercise of Multics on the new HIS 6180 computer are presented. The report concludes that Multics as implemented today is not certifiably secure and cannot be used in an open use multilevel system- However, the Multics security design principles are significantly better than other contemporary systems. Thus, Multics as implemented today, can be used in a benign Secret/Top Secret environment . In addition, Multics forms a base from which a certifiably secure open use multi-level system can be developed. 

References

Paul A. Karger and Roger R. Schell, MULTICS Security Evaluation: Vulnerability Analysis, ESD-TR-74-193 Vol. II, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (June 1974).

https://csrc.nist.gov/CSRC/media/Publications/conference-paper/1998/10/08/proceedings-of-the-21st-nissc-1998/documents/early-cs-papers/early-cs-papers-1970-1985.pdf

Related papers

Ken Thompson, “Reflections on Trusting Trust,” Communications of the ACM 27(8) pp. 761-763 (Aug. 1984); Turing Award lecture.