Orange Book n. The U.S. Government's standards document
"Trusted Computer System Evaluation Criteria, DOD standard
5200.28-STD, December, 1985" which characterize secure computing
architectures and defines levels A1 (most secure) through D
(least). Stock UNIXes are roughly C1, and can be upgraded to about
C2 without excessive pain. See also {{crayola books}}, {{book
titles}}.