Classified information
material that government claims requires confidentiality / From Wikipedia, the free encyclopedia
Classified information is sensitive information to which access is restricted by law or regulation to particular classes of people. A formal security clearance is required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation. There are usually several levels of sensitivity, with differing clearance requirements. This sort of hierarchical system of sharing information among a group of people is used by most national governments. Deciding the level of sensitivity of data is called data classification.
The purpose of classification is to protect information from being used to damage or cause danger to national security. Classification says what is a "state secret" and deals with different levels of protection based on the damage the information might cause if it reached the wrong hands.
Some non-government organizations and corporations also have their own secret information, normally referred to as trade secrets.