On DOS systems, deleting a file involves deleting the first character of an index pointing file. This indicates to the computer that the space (sectors) are again available for use. Moving a file to another location occurs in applications programs nearly every time the data is saved. This is because in most programs, the old file is deleted only after the new file is saved.
Unused sector space is also a problem. If a new file is written to a sector previously used to store other data, the new data only overwrites the previous locations until it is fully stored. Any data taking up more space than the new file will remain on the disk, even though not available for use again.
The third problem involves computers which temporarily store data to a hard drive as part of an application program operation, or during automatic timed backup. This process is a means of protecting work from accidental program failure.Any time data is stored to a hard drive or floppy it can be recovered unless overwritten or degaussed in a specific way.
For removable drives or floppies that have actually stored classified information, the same process is acceptable if the disk is to be reused. However, the cleared disk must be protected securely and can only be reused to store information at the same level of classification as it previously held. When the asset is declassified, the hard drive or floppy must be degaussed. It is the users responsibility to coordinate degaussing with the NRL IS Security Group and the NRL Locksmith Shop. The degausser is located in the NRL locksmith shop.