Data destruction is the process of destroying data stored on tapes, hard disks and other forms of electronic media so that it is completely unreadable and cannot be accessed or used for unauthorized purposes.
When data is deleted, it is no longer readily accessible by the operating system or application that created it. But deleting a file is not enough; data destruction software must be used to overwrite the available space/blocks with random data until it is considered irretrievable.
Data can also be destroyed through degaussing, which destroys data on magnetic storage tapes and disk drives by changing the magnetic field. One caveat with this method is that the person who wishes to destroy data will need to know the exact strength of degaussing needed for each tape type and drive. Storage media can also be destroyed by using a mechanical device called a shredder to physically mangle tape, optical media and hard disk drives.
See also: hard drive overwriter, hard drive shredder, wipe, remote wipe, enterprise wipe