Which media control below is the BEST choice to prevent data remanence on magnetic tapes or floppy disks?

Which media control below is the BEST choice to prevent data remanence on magnetic tapes or
floppy disks?

A.
Applying a concentration of hydriodic acid (55% to 58% solution) to the gamma ferric oxide disk
surface

B.
Overwriting the media with new application data

C.
Degaussing the media

D.
Making sure the disk is re-circulated as quickly as possible to prevent object reuse

Explanation:
Degaussing is recommended as the best method for purging most magnetic mediA. Degaussing is a
process whereby the magnetic media is erased, i.e., returned to its initial virgin statE. Erasure via
degaussing may be accomplished in two ways: In AC erasure, the media is degaussed by applying an
alternating field that is reduced in amplitude over time from an initial high value (i.e., AC-powered)
In DC erasure, the media is saturated by applying a unidirectional field (i.e., DC-powered or by
employing a permanent magnet) Another point about degaussing: Degaussed magnetic hard drives
will generally require restoration of factory-installed timing tracks, so data purging is recommendeD.
Also, physical destruction of CDROM or WORM media is required. *Answer ” Overwriting the media
with new application data” is not recommended because the application may not completely
overwrite the old data properly, and strict configuration controls must be in place on both the
operating system and the software itselF. Also, bad sectors on the media may not permit the
software to overwrite old data properly. To satisfy the DoD clearing requirement, it is sufficient to
write any character to all data locations in question (purging). To purge the media, the DoD requires
overwriting with a pattern, then its complement, and finally with another pattern; e.g., overwrite
first with 0011 0101, followed by 1100 1010, then 1001 0111. The number of times an overwrite
must be accomplished depends on the storage media, sometimes on its sensitivity, and sometimes
on differing DoD component requirements, but seven times is often recommended. *Answer
“Applying a concentration of hydriodic acid (55% to 58% solution) to the gamma ferric oxide disk
surface” is a rarely used method of media destruction, and acid solutions should be used in a wellventilated area only by qualified personnel. *Answer “Making sure the disk is re-circulated as quickly
as possible to prevent object reuse” is wrong. Source: NCSC-TG-025 A Guide to Understanding Data
Remanence in Automated Information Systems.