Page 1521 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

environments. Erasing the media performs a delete, but the data
remains and can easily be restored. Clearing, or overwriting, writes

unclassified data over existing data, but some sophisticated
forensics techniques may be able to recover the original data, so
this method should not be used to reduce the classification of
media.

6. C. Sanitization can be unreliable because personnel can perform
the purging, degaussing, or other processes improperly. When

done properly, purged data is not recoverable using any known
methods. Data cannot be retrieved from incinerated, or burned,
media. Data is not physically etched into the media.

7. D. Purging is the most reliable method of the given choices.
Purging overwrites the media with random bits multiple times and
includes additional steps to ensure that data is removed. While not
an available answer choice, destruction of the drive is a more

reliable method. Erasing or deleting processes rarely remove the
data from media, but instead mark it for deletion. Solid state drives
(SSDs) do not have magnetic flux, so degaussing an SSD doesn’t
destroy data.

8. C. Physical destruction is the most secure method of deleting data
on optical media such as a DVD. Formatting and deleting processes
rarely remove the data from any media. DVDs do not have

magnetic flux, so degaussing a DVD doesn’t destroy data.

9. D. Data remanence refers to data remnants that remain on a hard
drive as residual magnetic flux. Clearing, purging, and overwriting
are valid methods of erasing data.

10. C. Linux systems use bcrypt to encrypt passwords, and bcrypt is
based on Blowfish. Bcrypt adds 128 additional bits as a salt to
protect against rainbow table attacks. Advanced Encryption
Standard (AES) and Triple DES (or 3DES) are separate symmetric

encryption protocols, and neither one is based on Blowfish, or
directly related to protecting against rainbow table attacks. Secure
Copy (SCP) uses Secure Shell (SSH) to encrypt data transmitted
over a network.