High Quality Content by WIKIPEDIA articles! Classified information is a categorization applied to information that a government claims is sensitive information. Access is restricted by law or regulation to particular groups of persons. A formal security clearance is often required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation. There are typically several levels (classes) of sensitivity, with differing clearance requirements. This sort of hierarchical system of secrecy is used by virtually every national government. The act of assigning the level of sensitivity to data is called data classification. Although the root sense of the word "classified" is simply synonymous with "categorized", it has developed a sense synonymous with "censored" in the context of classified information.