It's pretty obvious why the DOD may want to ensure that defense secrets are erased beyond recovery when hardware and software are disposed of. But what about the rest of us? Why would we need to erase beyond discovery?
Well, please take a read of my article, Permanently Delete Files So Personal Information Is Irrecoverable, to understand why you should take special measures to guard privacy.
Most people believe that they do permanently delete their data. However, clicking delete, emptying the Recycle Bin or even formatting the drive doesn't get rid of files. The digital information still remains on the drive we are using. This is known as data remanence -- the residual representation of data that remains even after attempts have been made to remove or erase the data.So, when we delete, it's simply the pathway to the file(s) that's removed from the file system directory -- the data itself is reserved for overwriting with new content. However, even when the data is overwritten, the whole file may not be filled and these remnants can be recovered to form a pretty good picture of what was there before.
Let's have a look at where the DOD 5220.22 comes in...
Several standards exist for the secure removal of data and data remanence. Many countries have developed sanitisation processes which include, specific overwriting techniques, degaussing, encryption and physical destruction.
In the United States, DoD 5220.22-M is the policy document for all standards regarding security. If you visit 'DoD Issuances' (The Official Department of Defense Website for DoD Issuances), you will see the most recent issuance of DoD 5220.22-M, February 28, 2006 (see also DTM-09-019), National Industrial Security Program Operating Manual (NISPOM).
This is a massive tomb and covers...
Under Chapter 8, 'Information System Security', Section 3. 'Common Requirements', there are the following clauses:
"8-301. Clearing and Sanitization. Instructions on clearing, sanitization and release of IS media shall be issued by the accrediting CSA.
a. Clearing. Clearing is the process of eradicating the data on media before reusing the media in an environment that provides an acceptable level of protection for the data that was on the media before clearing. All internal memory, buffer, or other reusable memory shall be cleared to effectively deny access to previously stored information.
b. Sanitization. Sanitization is the process of removing the data from media before reusing the media in an environment that does not provide an acceptable level of protection for the data that was in the media before sanitizing. IS resources shall be sanitized before they are released from classified information controls or released for use at a lower classification level."
The work of Wright et al. Overwriting Hard Drive Data: The Great Wiping Controversy showed that a single wipe of a modern drive was sufficient to prevent forensic recovery of data.
I go into more detail about this software in my article, Permanently Delete Files with CyberScrub.