Data at rest is a term that is sometimes used to refer to all data in computer storage while excluding data that is traversing a network or temporarily residing in computer memory to be read or updated. Data at rest can be archival or reference files that are changed rarely or never; data at rest can also be data that is subject to regular but not constant change. Examples include vital corporate files stored on the hard drive of an employee's notebook computer, files on an external backup medium, files on the servers of a storage area network (SAN), or files on the servers of an offsite backup service provider.
Businesses, government agencies, and other institutions are concerned about the ever-present threat posed by hackers to data at rest. In order to keep data at rest from being accessed, stolen, or altered by unauthorized people, security measures such as data encryption and hierarchical password protection are commonly used. For some types of data, specific security measures are mandated by law.