Information systems security attempts to account for problems presented by certain aspects inherent in the use of computers. For example, the sharing of hardware across computing processes presents a particular set of problems. The difficulties of information systems security began to be identified during the 1960s, when concurrent sharing of computers began. Computers had been shared among applications and users almost from the beginning. Because few jobs used all of the resources of the computer and because of the very high cost of those resources, users immediately began to look for ways to better exploit their use by sharing the computer concurrently across multiple jobs or users.
Data sharing permits information to be transferred from one individual to another.
Although this sharing of data represents an increase in the value and utility of the data, there is a corresponding reduction in its confidentiality. In addition, the power, generality, flexibility, scope, and complexity of the modern computer make it error prone and increase the difficulty of determining how it was intended to be used. Most of the behavior of a modern computer is controlled by its stored program. For example, if the programmer fails to anticipate and provide for every possible input, the program may cause the computer to behave in an unanticipated way. Because the behavior of the computer is so complex, it is often difficult to determine whether the computer is performing as intended.