Exam CISA Topic 3 Question 732 Discussion

Section: Protection of Information Assets
Explanation:
Deleting and formatting does not completely erase the data but only marks the sectors that contained files
as being free. There are tools available over the Internet which allow one to reconstruct most of a hard
disk's contents. Overwriting a hard disk at the sector level would completely erase data, directories, indices
and master file tables. Reformatting is not necessary since all contents are destroyed. Overwriting several
times makes useless some forensic measures which are able to reconstruct former contents of newly
overwritten sectors by analyzing special magnetic features of the platter's surface. While hole-punching
does not delete file contents, the hard disk cannot be used anymore, especially when head parking zones
and track zero information are impacted. Reconstructing data would be extremely expensive since all
analysis must be performed under a clean room atmosphere and is only possible within a short time frame
or until the surface is corroded. Data reconstruction from shredded hard disks is virtually impossible,
especially when the scrap is mixed with other metal parts. If the transport can be secured and the
destruction be proved as described in the option, this is a valid method of disposal.