The following real-life passage illustrations this idea:
Jack V., a computer consultant from Brighton, bought a used notebook
computer for $400.00 at the clearance sale of a bankrupt Internet company.
It was clear that the hard disk drive contained data about the company. This
data included social security numbers and salary levels of the company’s
forty-six employees, plus pay roll records, strategic company plans,
confidential board of directors minutes, and other internal documents.
There have been many cases like this concerning the sales and purchase of
used computer.
6.1.2 Data Deletion by Means of an Operating Systems
There is a considerable difference between file deletion with operating
systems (with the help of file managers) and data destruction with the help
of specialized erasing programs.
The point is that operating systems, such as Windows, do not materially
delete anything from a hard disk when deleting a file: the name of the deleted
file in the File Allocation Table (FAT) is substituted by the name which is not
assumed as a correct one by the operating system. The file only becomes
invisible for a user and the cluster chain that contains file data is considered
to be free. But the information contained within the hard disk sectors stays
permanent. It is not very difficult for someone to recover it.
File deletion under the Linux operating system is somewhat more reliable,
but even in this case it is possible to obtain software tools to recover any
important information.
Neither partitions deletion on a disk nor even disk formatting solves this
problem. When partitions are deleted on a hard disk the information of
Partition table (if it is a primary partition) or File Allocation Table is deleted.
The information contained within sectors however remains untouched and
can be recovered with the help of software tools.
Reliable information destruction on hard disks is possible only while using
specially designed programs that implement specially designed erasing
algorithms.
48 Chapter 6 : Disk Data Wiping
