When data collects in one place, it is known as data at rest. This data is stable and inactive, and therefore cannot travel across a network or within the system. When at rest, data can be stored on hard drives, backup tapes, in offsite cloud backup and on mobile devices. As it is not moving through any networks, it is not being operated by any application. Data at rest should always be encrypted and where possible additional layers of security should be put in place, such as multi-factor authentication, cloud antivirus and both digital and physical access controls.