Measures to reduce security threats - general controls
Contingency planning

It is desirable for an organisation to prepare for a major disaster. This is called a "contingency plan" and its purpose is to enable the organisation to process data while computer equipment is being replaced and computer files are being reconstructed.
Elements in the disaster plan include alternative methods of data collection the use of alternative computer equipment the use of backup computer files temporary distribution of information
With respect to data corruption, data-file and database backup plans are devised, backup, recovery and emergency procedures exist

Grandfather-father-son: typically used with sequential systems.
Fall back and recovery: periodically the contents of files are copied onto a backup medium. If files are destroyed, the contents are reconstructed from the backup plus the transaction log or file.

Backups of all master files are taken at appropriate intervals (perhaps every Friday night, perhaps with every update). This may not be a full copy of the file but just those changes, which have been made since the last backup.
Copies of transaction files are kept for a given length of time eg 4 weeks.
Lists of masterfile information may be printed regularly and held in the safe (ie on hardcopy)
Different generations of important files are kept in different places - eg first level, a safe in the computer room, second level, a safe in the main office, third level, a safe in the building across the road.
NB: this must be well documented so the correct transactions are matched against the correct master when the recovery runs are under way - and none of this is any use unless the door to the fireproof safe is actually shut.
In on-line, real-time processing, actual duplicate copies of the master file may be necessary, with the duplication being enacted every 5 minutes, and every transaction in the meantime being logged; major users would even have 2 processors capable of acting - the second picking up automatically if the first goes down.

Backup:
Relating to procedures, equipment or data available in the event of failure or overloading.
Fall-back:
Backup systems brought into use in an emergency situation, especially the reserve database and programs that would be switched in quickly, or even automatically, in the event of a detected fault in a real-time system.
Recovery:
Re-instating backup after an error, or failure has occurred.