In computing, precautions taken to prevent the loss or misuse of data, whether accidental or deliberate. These include measures that ensure that only authorized personnel can gain entry to a computer system or file, and regular procedures for storing and “backing up” data, which enable files to be retrieved or recreated in the event of loss, theft, or damage.
A number of verification and validation techniques may also be used to prevent data from being lost or corrupted by misprocessing.
Encryption involves the translation of data into a form that is meaningless to unauthorized users who do not have the necessary decoding software.
Passwords can be chosen by, or issued to, individual users. These secret words (or combinations of alphanumeric characters) may have to be entered each time a user logs on to a computer system or attempts to access a particular protected file.
Physical access to the computer facilities can be restricted by locking entry doors and storage cabinets.
Master files (files that are updated periodically) can be protected by storing successive versions, or generations, of these files and of the transaction files used to update them. The most recent version of the master file may then be recreated, if necessary, from a previous generation. It is common practice to store the three most recent versions of a master file (often called the grandfather, father, and son generations).
Direct-access files are protected by making regular dumps, or back-up copies. Because the individual records in direct-access files are constantly being accessed and updated, specific generations of these files cannot be said to exist. The files are therefore dumped at fixed time intervals onto a secure form of backing store. A record, or log, is also kept of all the changes made to a file between security dumps.
Fireproof safes are used to store file generations or sets of security dumps, so that the system can be restarted on a new computer in the event of a fire in the computer department.
Write-protect mechanisms on discs or tapes allow data to be read but not deleted, altered, or overwritten. For example, the protective case of a 3˝-inch floppy disc has a write-protect tab that can be slid back with the tip of a pencil or pen to protect the disc’s contents.