Editing Data remanence (section)

====Feasibility of recovering overwritten data====

[[Peter Gutmann (computer scientist)|Peter Gutmann]] investigated data recovery from nominally overwritten media in the mid-1990s. He suggested [[magnetic force microscopy]] may be able to recover such data, and developed specific patterns, for specific drive technologies, designed to counter such.<ref name="Gutmann">{{cite journal|title=Secure Deletion of Data from Magnetic and Solid-State Memory|author=Peter Gutmann|date=July 1996|url=http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html|access-date=2007-12-10}}</ref> These patterns have come to be known as the [[Gutmann method]]. Gutmann's belief in the possibility of data recovery is based on many questionable assumptions and factual errors that indicate a low level of understanding of how hard drives work.<ref>{{Cite web|url=https://kaleron.edu.pl/throwing-Gutmanns-algorithm-into-the-trash.php|title=Throwing Gutmann's algorithm into the trash - about effectiveness of data overwriting.|website=kaleron.edu.pl}}</ref>

Daniel Feenberg, an economist at the private [[National Bureau of Economic Research]], claims that the chances of overwritten data being recovered from a modern hard drive amount to "urban legend".<ref>{{cite journal|title=Can Intelligence Agencies Recover Overwritten Data?|author=Daniel Feenberg|url=http://www.nber.org/sys-admin/overwritten-data-gutmann.html|access-date=2007-12-10}}</ref> He also points to the "[[18½ minute gap|{{frac|18|1|2}}-minute gap]]" [[Rose Mary Woods]] created on a tape of [[Richard Nixon]] discussing the [[Watergate break-in]]. Erased information in the gap has not been recovered, and Feenberg claims doing so would be an easy task compared to recovery of a modern high density digital signal.

As of November 2007, the [[United States Department of Defense]] considers overwriting acceptable for clearing magnetic media within the same security area/zone, but not as a sanitization method. Only [[#Degaussing|degaussing]] or [[#Physical destruction|physical destruction]] is acceptable for the latter.<ref name=DSSmatrix>{{cite web|url=http://www.oregon.gov/DAS/OP/docs/policy/state/107-009-005_Exhibit_B.pdf?ga=t| title=DSS Clearing & Sanitization Matrix|publisher=[[Defense Security Service|DSS]]| format=PDF|date=2007-06-28|access-date=2010-11-04}}</ref>

On the other hand, according to the 2014 [[NIST]] Special Publication 800-88 Rev. 1 (p.&nbsp;7): "For storage devices containing ''magnetic'' media, a single overwrite pass with a fixed pattern such as binary zeros typically hinders recovery of data even if state of the art laboratory techniques are applied to attempt to retrieve the data."<ref>{{cite journal
 | url = https://csrc.nist.gov/publications/detail/sp/800-88/rev-1/final
 | title = Special Publication 800-88 Rev. 1: Guidelines for Media Sanitization
 | publisher = [[National Institute of Standards and Technology|NIST]]
 | date = December 2014 | doi = 10.6028/NIST.SP.800-88r1
 | access-date = 2018-06-26
| last1 = Kissel
 | first1 = Richard
 | last2 = Regenscheid
 | first2 = Andrew
 | last3 = Scholl
 | first3 = Matthew
 | last4 = Stine
 | first4 = Kevin
 | doi-access = free
 }}</ref> An analysis by Wright et al. of recovery techniques, including magnetic force microscopy, also concludes that a single wipe is all that is required for modern drives. They point out that the long time required for multiple wipes "has created a situation where many organizations ignore the issue [altogether] – resulting in data leaks and loss."<ref>{{cite book
 | first = Craig | last = Wright
 |author2=Kleiman, Dave
 |author2-link=Dave Kleiman
 |author3=Shyaam, Sundhar R.S.
 | title = Information Systems Security | chapter = Overwriting Hard Drive Data: The Great Wiping Controversy | series = Lecture Notes in Computer Science | publisher = Springer Berlin / Heidelberg | isbn = 978-3-540-89861-0 | doi = 10.1007/978-3-540-89862-7_21
 | pages = 243–257 |date=December 2008
| volume = 5352 }}</ref>