We are always under the impression that formatting of a HDD or USB removes the data permanently. But this is not the truth. Data on these media can be retrieved by special disk / file recovery utilities and laboratory attacks even after formatting. Let us see what the best method of sanitizing data is.
Sanitization can be categorized into methods viz. (i) Clearing (ii) Purging and (iii) Physical Destruction.
(i) Clearing: This method involves the usage software or hardware products to overwrite storage space on the media with non-sensitive data. This process may include overwriting not only the logical storage location of a file(s) (e.g., file allocation table) but also may include all addressable locations. This method does not allow information retrieval by data, disk or file recovery utilities. This process is also known as ‘data wiping’.
(ii) Purging: This method of sanitization renders sanitized data unrecoverable by laboratory attack methods. Degaussing is a purging method. But this is not effective for optical media like CDs and DVDs
(iii) Physical Destruction: This is the ultimate method of destroying media permanently. This is the only method available for CDs ad DVDs for permanent disposal of data.
The following table lists the sanitization method for various media under the 3 sanitization levels.
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