Computer security has been a topic of great importance since the emergence of second generation main frame computers (early 1960's). Some of the earliest applications of these main frame machines involved financial calculations. Floating point arithmetic was often used to represent (inexactly) the values of a penny or dime. More than one dishonest programmer developed software which would accumulate the inaccuracy of each account transaction into a single account. The losses were not noticed on individual accounts, but were later noticed at the institutional level.
In the early 1960's, as the first time-sharing/multi-user systems were being developed, system designers realized that they had to give serious consideration to security designs because these systems allowed remote access to the computer which were not covered by the physical security measures protecting the computer.
Donn Parker, of SRI, emerged as an international computer security expert during the late 1970's and early 1980's. His book, Fighting Computer Crime [Park 83], though published in 1983, prior to the Internet as known today, describes a variety of techniques for achieving secure networked systems.