Erasing confidential data

Modern methods of data encryption are deterring unwanted network attackers from extracting sensitive data from stored database files. Attackers who want to retrieve confidential data are becoming more resourceful by looking into places where data might be stored temporarily. A hard drive on a local network node, for example, can be a prime target for such a search. One avenue of attack is the recovery of data from residual data on a discarded hard disk drive. When deleting confidential data from hard drives, removable floppies or USB devices, it is important to extract all traces of the data so that recovery is not possible.

Most official guidelines around disposing of confidential magnetic data do not take into account the depth of today’s recording densities, nor the methods used by the operating system when removing data. For example, the Windows DELETE command merely changes the file name so that the operating system will not look for the file. The situation with NTFS is similar.

Removal of confidential personal information or company trade secrets in the past might have used the FORMAT command or the DOS FDISK command. Ordinarily, using these procedures give users a sense of confidence that the data has been completely removed.

When using the FORMAT command, Windows displays a message like this:

The FORMAT utility actually creates new FAT and ROOT tables, leaving all previous data on the disk untouched. Moreover, an image of the replaced FAT and ROOT tables are stored, so that the UNFORMAT command can be used to restore them.

As well, FDISK merely cleans the Partition Table (located in the drive's first sector) and does not touch anything else.