Why can’t I just use the DELETE command?

Although using the DELETE command may be the quickest and most convenient method of “erasing” data, deleting merely removes the index entry and pointers to the data.  The actual data remains on the hard drive.  There are some DELETE programs that will overwrite the sectors used by a file.  These programs are an improvement, but they still pose a problem.  Most application programs and operating systems will open temporary or swap/cache files while working on the data.  When the program is closed, the application “deletes” these temp files.  So even if the original file has been overwritten, multiple copies of the raw data may still exist on the hard drive.

What if I FORMAT the hard drive?

Using the FORMAT command merely creates a new blank indexing scheme for the operating system, making all the sectors available for new files.  Again, the actual data remains on the hard drive.

Isn’t degaussing the hard drive better?

Degaussing is the use of an external de-magnetizer designed to reduce any magnetic recordings on the media and is an acceptable and effective method.  However, today’s hard disks rely on magnetically recorded servo-patterns to allow control and movement of the read/write head assembly and the rotation speed of the platters.  Any degaussing powerful enough to remove the data would most certainly destroy the servo; effectively rendering the hard drive non-functional.

What about overwriting the data?

Overwriting of the data means replacing the currently stored data with a predetermined pattern of meaningless information.  This has become an accepted and effective means of rendering data unrecoverable.  To accomplish this, the process must be correctly understood and carefully implemented.   For all practical purposes, if data is “successfully” overwritten, even a single time, it can be considered as unreadable.

Are there problems with Overwriting Data?

If you still want to have a usable hard drive after the removal of data, the only alternative is to utilize overwrite techniques.  The reliability of overwriting hard drives is not straightforward and generally requires a good deal of technical expertise.  There are three main areas of concern with overwriting as a method of data erasure: Human error or misuse of the software; Failure of the software to write to all addressable disk space; and Track-edge phenomena Notwithstanding of these concerns, the process of overwriting data, if correctly implemented, is by far the most secure and economical method of erasing data from a hard drive.

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