Data Remanence

Definition

Data remanence is the ability of computer memory to retain previously stored information beyond its intended lifetime.

Application

With many data storage techniques, information can be recovered using specialized techniques and equipment even after it has been overwritten; examples include:

• Write heads used on exchangeable media (e.g., floppy disks, magstripe cards) differ slightly in position and width due to manufacturing tolerances. As a result, one writer might not overwrite the entire area on a medium that had previously been written to by a different device. Normal read heads will only give access to the most recently written data, but special high-resolution read techniques (e.g., magnetic-force microscopy) can give access to older data that remains visible near the track edges.

• Even with a perfectly positioned write head, the hysteresis properties of ferromagnetic media can result in a weak form of previous data to remain recognizable in overwritten areas. This...