Data left as a result of incomplete or inadequate deletion is
gathered. Examples include object reuse attacks like the DOS undelete
command in insecure operating systems, electromagnetic analysis of deleted
media to regain deleted bits, and electron microscopy techniques used to
extract overwritten data.
Complexity: Residual data gathering in the case
of simple undeletions or allocating large volumes of space and examining
their content is straightforward. Looking for residual data on magnetic media
using electromagnetic measurements and electron microscopy is somewhat m,ore
complex and requires statistical analysis and correlation of signals in a
signal processing component. While this is not trivial, it is within the
capability of most electrical engineers and electronics specialists.