Chapter - 15
Programming for Data Wipers
Introduction
We have already that discussed when we delete any file from the disk, the information is not erased completely from the drive but it is marked as available for new data to be written over it.
When we format a drive, all the information of files and directories of the drive such as FATs and Root Directory Entries are wiped out but data area remains unchanged and nothing from data area of the disk is erased.
The data which is deleted or formatted using the operating system remains on the data area as it is and can be recovered with some data recovery efforts and data recovery software.
Therefore the need to fully eliminate data from a drive leads the requirement for such a program that wipes out the data from the disk completely. For doing this it is not sufficient to just delete the files or just to format the drive but the data on the disk must be overwritten by some other data.
The programs which are used to wipe out the data completely from the disk are known as the data wiping programs. These programs write random characters on the data area to overwrite data and to wipe out all the information previously saved on the disk.
When the data becomes completely unrecoverable
To wipe out the data, the data area of the disk should be overwritten by some other data on it but the problem does not end here. To further complicate things, the tendency of magnetic drives to remember data that has been overwritten requires that data also be over-written several times by random sequences of data so that it may not be recovered even with sophisticated data recovery tools.
It is so because the technologies which can recover data even after the use of some simple data wipers are available today.
Some data erasure products perform binary zeros and binary ones overwriting on data. Writing a series of binary zeros and binary ones achieves the deepest overwrite effect as these values are the minimum and maximum magnetic values respectively.
Although this is the theory of an ideal data wiping program, but generally, the data over writing by random ASCII character is sufficient. The reason to say so is that the recovery by sophisticated recovery tools and technology can not be used to recover the data of any organization for a routine data recovery because these technologies are very much expensive and cost in millions even for single recovery. Not only this but also these technologies are available only in few countries around the world.
We shall discuss only the simple data overwriting to wipe the data from the disk. However you can further modify the same programs to write the random characters only with some little efforts. Data wiped out by this idea can also not be recovered by any data recovery software.
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