Degaussing

Degaussing is the removal or reduction of a magnetic field of a disk or drive, using a device called a degausser that that has been designed for the media being erased. Applied to magnetic media, degaussing may purge an entire media element quickly and effectively.

Degaussing often renders hard disks inoperable, as it erases low-level formatting that is only done at the factory during manufacturing. Degaussed floppy disks can generally be reformatted and reused, though.

In some high-security environments, one may be required to use a degausser that has been approved for the task.