It has been suggested that File wipe be merged into this article or section. (Discuss) Data remanence is the residual physical representation of data that has been in some way erased. After storage media is erased there may be some physical characteristics that allow data to be reconstructed. As early as 1960 the problem caused by the retentive properties of computer storage media was recognized. It was known that without the application of data removal procedures, inadvertent disclosure of sensitive information was possible should the storage media be released into an uncontrolled environment. Degaussing, overwriting, data encryption, and media destruction are some of the methods that have been employed to safeguard against disclosure of sensitive information. Over a period of time, certain practices have been accepted for the clearing and purging of storage media. Image File history File links Please see the file description page for further information. ...
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The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ...
1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ...
Degaussing is the process of reducing or eliminating an unwanted magnetic field. ...
In cryptography, encryption is the process of obscuring information to make it unreadable without special knowledge. ...
Clearing
Clearing is the removal of sensitive data from storage devices in such a way that there is assurance, proportional to the sensitivity of the data, that the data may not be reconstructed using normal system capabilities, i.e., through the keyboard. (This may include use of data recovery utilities and advanced diagnostic routines.) Data recovery is the process of recovering data from primary storage media when it cannot be accessed normally. ...
Clearing can be used when the secured physical environment (where the media was used) is maintained. In other words, the media is reused within the same computer and environment previously used.
In an operational computer, clearing can usually be accomplished by an overwrite of unassigned system storage space, provided the system can be trusted to provide separation of the storage space and unauthorized users. For example, a single overwrite of a file or all system storage, if the circumstance warrants such an action, is adequate to ensure that previous information cannot be reconstructed through a keyboard attack, provided the system can be trusted to provide separation of system resources and unauthorized users. Software used for clearing should be under strict configuration controls. Note: Simply removing pointers to a file, which is all that occurs when a file is deleted in most operating systems, will not generally render the previous information unrecoverable through normal system capabilities. Likewise, reformatting, repartitioning, reghosting or reimaging a system is not guaranteed to write to every area of the disc, even though it will cause the disc to appear as empty to most programs. In information technology and telecommunications, the term configuration management or configuration control has the following meanings: The management of security features and assurances through control of changes made to hardware, software, firmware, documentation, test, test fixtures and test documentation of an automated information system, throughout the development and operational life...
An operating system (OS) is an essential software program that manages the hardware and software resources of a computer. ...
Purging Purging is the removal of sensitive data from a system or storage device in such a way that there is assurance, proportional to the sensitivity of the data, that the data may not be reconstructed through open-ended laboratory techniques. A computer must be disconnected from any external network before a purge. Purging must be used when the secured physical environment (where the media was used) will not be maintained. In other words, media scheduled to be released from a secure facility to a non-secure facility or environment should be purged.
The United States Department of Defense (DoD) has approved both overwriting and degaussing for purging data, although the effectiveness of overwriting cannot be guaranteed without examining each specific situation. DoD documents often refer to purging as "sanitization". The United States Department of Defense, abbreviated as DoD or DOD and sometimes called the Defense Department, is a civilian Cabinet organization of the United States government. ...
Degaussing is the process of reducing or eliminating an unwanted magnetic field. ...
Software for purging To purge the AIS storage media, the DoD requires overwriting multiple times in a prescribed pattern. The number of times an overwrite must be accomplished depends on the storage media, sometimes on its sensitivity, and sometimes on differing DoD component requirements. Software developers must design the software such that the software continues to write to all addressable locations on the media, in spite of intermediate errors. All such errors in usable sectors should be reported with a listing of current content. Unusable sectors must be completely overwritten, because the unusable sector list will not show whether the sector ever contained any sensitive data. If any errors occur while overwriting or if any unusable sector could not be overwritten, then degaussing is required.
There are additional risks to trusting overwrite software to purge disks. The environment in which the software must operate is difficult to constrain. For this reason, care must be exercised during software development to ensure the software cannot be subverted. The overwrite software should be protected at the level of the media it purges, and strict configuration controls should be in place on both the operating system the software must run under and the software itself. The overwrite software must be protected from unauthorized modification.
Despite its issues, software-based data destruction methods are inexpensive and easy to use for the average computer user. Darik's Boot and Nuke is an open source, GPL-licensed data destruction program that fits on a single 3.5 inch floppy disk. Its programmers claim that, when used on boot media, the program can reliably destroy all data on IDE and SCSI hard drives. This is intended to defeat most forensic data recovery methods and bring the program into compliance with United States Department of Defense and Royal Canadian Mounted Police standards, among others. Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ...
The GNU logo Wikisource has original text related to this article: GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a controversial, yet the most popular free software license, originally written by Richard Stallman for the GNU project (GNU itself is a recursive acronym...
A floppy disk is a data storage device that is composed of a ring of thin, flexible (i. ...
It has been suggested that System partition and boot partition be merged into this article or section. ...
See Integrated Development Environment (IDE) Integrated_development_environment Binomial name Leuciscus idus Linnaeus, 1758 The ide or orfe, Leuciscus idus, is a freshwater fish of the family Cyprinidae found across northern Europe and Asia. ...
SCSI stands for Small Computer System Interface, and is a standard interface and command set for transferring data between devices on both internal and external computer buses. ...
Forensic science (often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. ...
Data recovery is the process of recovering data from primary storage media when it cannot be accessed normally. ...
The United States Department of Defense, abbreviated as DoD or DOD and sometimes called the Defense Department, is a civilian Cabinet organization of the United States government. ...
Royal Canadian Mounted Police heraldic badge. ...
Standard patterns for purging - DoD 5220.22-M prescribes overwriting data in 3 passes: with a character, then its complement, and finally with a random character; e.g., overwrite first with 0000 0000, followed by 1111 1111, then 1001 0111.
- NAVSO P5239-26 standards are more rigorous versions of the same procedure.
- Another DoD standard allegedly prescribes overwriting data in 7 passes.
- Gutmann suggests overwriting data in 35 passes.
When most computers delete a file it does not actually remove the contents of the file but rather simply unlinks the file from the file directory system, leaving the contents of the file in the disk sectors. ...
The bad track problem A compromise of sensitive data may occur if media is released when an addressable segment of a storage device (such as unusable or "bad" tracks in a disk drive or inter-record gaps in tapes) is not receptive to an overwrite. As an example, a disk platter may develop unusable tracks or sectors; however, sensitive data may have been previously recorded in these areas. It may be difficult to overwrite these unusable tracks. Before sensitive information is written to a disk, all unusable tracks, sectors, or blocks should be identified (mapped). During the life cycle of a disk, additional unusable areas may be identified. If this occurs and these tracks cannot be overwritten, then sensitive information may remain on these tracks. In this case, overwriting is not an acceptable purging method and the media should be degaussed or destroyed.
Degaussing Degaussing is a process whereby the magnetic media is erased. Degaussing requires a degausser device that is designed and approved for the type of media being purged. The U.S. General Services Administration maintains a list of approved degaussers. Degaussing is the process of reducing or eliminating an unwanted magnetic field. ...
This article needs to be updated. ...
Degaussing often renders hard drives inoperable. This can prevent computers from being recycled, say for educational use. The sensitivity of the data stored on the computer and the feasibility of software purging should be weighed before degaussing hard drives.
The DoD has approved overwriting for clearing, but not purging, magnetic floppy disks. Degaussing is the preferred method. Degaussed floppy disks can generally be reformatted and reused.
Disk encryption Several software products, including Apple's Mac OS X and PGP, can encrypt all data before it is stored on a hard disk or other storage medium. If enabled beginning when the computer is first purchased or first used for sensitive information, disk encryption can alleviate the need for degaussing and destruction. This article or section does not cite its references or sources. ...
PGP is a computer program which provides cryptographic privacy and authentication. ...
Systemic problems with clearing and purging in practical systems Disk storage systems in modern computers systems are both buffered at the disk and within typical operating systems. It is not, generally possible to have any assurance that a particular sector on disk has actually been written, as the data may have been buffered at the disk (or within the operating system) and not written prior to a power down or reset. In addition, some disk management software is intelligent and may notice that the same sector is being re-written several times, and simply cancel all but the last.
Despite overwrite of a disk sector, it has been shown that, with sufficient care and resources, the chance of recovering some or all of the supposedly erased and overwritten data is substantial. Peter Gutmann of the University of Auckland investigated this possibility in the middle '90s and his paper recounting his results is surprising. In light of this, it will be clear that intelligent buffering of sensitive data can, in some systems, be inadequate to render that data unavailable. Peter Gutmann is a computer scientist based in Auckland, New Zealand; he received his Ph. ...
The University of Auckland is New Zealands largest research-based university. ...
In addition, a similar recoverability has been observed in RAM, and it is therefore, generally, not possible to assume that removing the power from volatile RAM will always render the data stored in it unrecoverable. There are slow memory biasing mechanisms in some RAM circuits, usually connected to charge migration in semiconductor structures, which can retain data across such power cycling.
When the data being temporarily stored is of an extremely sensitive nature, such as cryptographic keys, considerable care is required, and must be based on the particular characteristics of the operating system, RAM, and long term storage in use. There is no universal solution, and for a particular system, there may be no solution at all which ensures data is unrecoverable. A key is a piece of information that controls the operation of a cryptography algorithm. ...
Operating systems which guarantee that a particular system call will securely erase and overwrite a specific block of memory, and disk drives which will guarantee that specific data will be committed to storage without optimization, and an interface which controls that mechanism will be required, at minimum. There are no readily available operating systems nor storage devices which provide such facilities.
Destruction It is good practice to purge media before submitting it for destruction. Media may generally be destroyed by one of the following methods: Image File history File linksMetadata Download high resolution version (2816x2112, 3587 KB) Summary Lorry of a paper shredding company. ...
Image File history File linksMetadata Download high resolution version (2816x2112, 3587 KB) Summary Lorry of a paper shredding company. ...
Paper shredding can be contracted out Outsourcing (or contracting out) is often defined as the delegation of non-core operations or jobs from internal production within a business to an external entity (such as a subcontractor) that specializes in that operation. ...
- Destruction at an approved metal destruction facility, i.e., smelting, disintegration, or pulverization.
- Incineration.
- Application of corrosive chemicals, such as acids, to recording surfaces.
- Application of an abrasive substance (emery wheel or disk sander) to a magnetic disk or drum recording surface. Make certain that the entire recording surface is completely removed before disposal. Also, ensure proper protection from inhaling the abraded dust.
Chemical reduction, or smelting, is a form of extractive metallurgy. ...
For other uses, see Acid (disambiguation). ...
An abrasive is usually a material that is used to smooth, machine, or, in some cases, roughen another softer material through extensive rubbing. ...
Emery (also known as iron spinel and hercynite) is a common impure variety of the mineral corundum. ...
After just three years of use dust has blocked this laptop heat sink, making the computer unusable Dust is a general name for minute solid particles with diameter less than 500 micrometers (otherwise see sand or granulates) and, more generally, for finely divided matter. ...
CDs, DVDs, etc. Optical media are not magnetic and cannot be erased by degaussing. Write-once media, such as CD-ROM, CD-R, DVD-R, etc., cannot be purged by software or a degausser. They must be destroyed. Read/write optical media, such as CD-RW and DVD-RW can be cleared by overwriting under software control. It is not known if such software purging is effective, and in any case, it would be a lengthy process. Destruction is usually the best approach. Some shredding machinery, even inexpensive commercial ones, can do so. The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ...
A CD-R (Compact Disc-Recordable) is a variation of the Compact Disc digital audio disc invented by Philips and Sony. ...
A DVD+R disc The title given to this article is incorrect due to technical limitations. ...
Compact Disc ReWritable (CD-RW) is a rewritable optical disc format. ...
The title given to this article is incorrect due to technical limitations. ...
A shredder is a machine that tears objects into smaller pieces. ...
Flash memory devices Data stored on devices that use flash memory, such as USB thumb drives and memory cards, can often be recovered even after it has been erased. No generally accepted method for disposing of these devices seems to be available. Data tends to "burn in" the longer it is stored. Overwriting with random data may be superior to erasing, especially if it can be done several times, each a week or more apart. Since these units are so small, secure storage until the original data is no longer sensitive may be the simplest approach. A USB Flash Memory Device. ...
A USB keydrive, shown with a US quarter coin for scale. ...
Source Adapted from National Computer Security Center TG-025.
See also - NAVSO P5239-26
- AFSSI-5020
- AR380-19
This article or section is missing references or citation of sources. ...
Data recovery is the process of recovering data from primary storage media when it cannot be accessed normally. ...
Forensic identification is the application of forensic science and technology to identification of specific objects from the traces they leave, often at a crime scene). ...
Paper shredder with wastebasket Paper shredding can be contracted out Paper shredders are used to cut paper into very fine strips or tiny paper chips. ...
The plain text term has a different meaning. ...
In cryptography, zeroisation (also spelled zeroization) is the practice of erasing sensitive parameters (especially keys) from a cryptographic module to prevent their disclosure if the equipment is captured. ...
AFSSI-5020 is the USAF Cryptologic Support Centers version of the DOD 5220. ...
AR 380-19 is the US Armys Information Systems Security version of the DOD 5220. ...
Purging Software Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ...
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