Browse Definitions :
Definition

slack space (file slack space)

Slack space is the leftover storage that exists on a computer’s hard disk drive when a computer file does not need all the space it has been allocated by the operating system. The examination of slack space is an important aspect of computer forensics.

To understand why slack space plays an important role in E-discovery, one must first understand how data is stored on computers that have hard disk drives. Computers with hard disk drives store data in a sealed unit that contains a stack of circular, spinning disks called platters. Each platter is composed of logically defined spaces called sectors and by default, most operating system (OS) sectors are configured to hold no more than 512 bytes of data. If a text file that is 400 bytes is saved to disk, the sector will have 112 bytes of extra space left over. When the computer’s hard drive is brand new, the space in a sector that is not used – the slack space – is blank, but that changes as the computer gets used.

When a file is deleted, the operating system doesn't erase the file, it simply makes the sector the file occupied available for reallocation. Should a new file that is only 200 bytes be allocated to the original sector, the sector’s slack space will now contain 200 bytes of leftover data from the first file in addition to the original 112 bytes of extra space. That leftover data, which is called latent data or ambient data, can provide investigators with clues as to prior uses of the computer in question as well as leads for further inquiries. In 2016, for example, the Federal Bureau of Investigation (FBI) revealed that it had reviewed millions of e-mail fragments that resided in the slack space of former Secretary of State Hillary Clinton’s personal servers in order to determine whether or not the servers have improperly stored or transmitted classified information.

Technically, a file’s slack space is the difference between its logical and physical size. The logical size of a file is determined by the file’s actual size and is measured in bytes. The physical size of a file is determined by the number of sectors that are allocated to the file. In most operating systems, including Windows, sectors are clustered in groups of four by default which means that each cluster has 2,048 bytes.

The logical size of the blue file below is 1280 bytes. This file was allocated a cluster of four 512-byte sectors, which means the physical size of the file is 2,048 bytes. The difference between 2,048 and 1,280 is 768, which means that the blue file’s slack space is 768 bytes.

This was last updated in July 2016

Continue Reading About slack space (file slack space)

SearchCompliance
  • ISO 31000 Risk Management

    The ISO 31000 Risk Management framework is an international standard that provides businesses with guidelines and principles for ...

  • pure risk

    Pure risk refers to risks that are beyond human control and result in a loss or no loss with no possibility of financial gain.

  • risk reporting

    Risk reporting is a method of identifying risks tied to or potentially impacting an organization's business processes.

SearchSecurity
  • Pretty Good Privacy (PGP)

    Pretty Good Privacy or PGP was a popular program used to encrypt and decrypt email over the internet, as well as authenticate ...

  • email security

    Email security is the process of ensuring the availability, integrity and authenticity of email communications by protecting ...

  • Blowfish

    Blowfish is a variable-length, symmetric, 64-bit block cipher.

SearchHealthIT
SearchDisasterRecovery
  • What is risk mitigation?

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • fault-tolerant

    Fault-tolerant technology is a capability of a computer system, electronic system or network to deliver uninterrupted service, ...

  • synchronous replication

    Synchronous replication is the process of copying data over a storage area network, local area network or wide area network so ...

SearchStorage
  • direct access

    In computer storage, direct access is the process of reading and writing data on a storage device by going directly to where the ...

  • kibi, mebi, gibi, tebi, pebi and exbi

    Kibi, mebi, gibi, tebi, pebi and exbi are binary prefix multipliers that, in 1998, were approved as a standard by the ...

  • holographic storage (holostorage)

    Holographic storage is computer storage that uses laser beams to store computer-generated data in three dimensions.

Close