Classified information
Classified information is material, collected or created by a government, that is subject to limitations on its release to the general public, has restrictions on its handling based on security concerns, and may have penalties for its unauthorized release. The general assumption is that the inappropriate disclosure of such information could do varying levels of harm to the national security of a nation, including diplomatic, military, and intelligence missions.
Other governmental information, including civilian law enforcement, privileged business information, personnel matters, medical records, etc., may have restrictions on access and distribution, but the term "classified" tends to be specific to national security. Also, businesses may have material that is "proprietary" and safeguarded internally as is classified material; governments may receive proprietary information and will be expected, within legal requirements, to protect it from disclosure.
Levels of sensitivity
General classification
Most countries have between two and five increasingly stringent levels of classification based on the harm that disclosure is predicted to cause. With increasing level, there will be more and more physical protection, more investigative requirements for security clearances to handle the material, and, in general, more restricted distribution.
A multinational hierarchy consists of (in the appropriate language), the following general levels:
| Typical descriptor | General sensitivity |
|---|---|
| UNCLASSIFIED | Releasable to the public |
| FOR OFFICIAL USE ONLY; SENSITIVE BUT UNCLASSIFIED | Restricted but not technically classified. For example, it might be used to give law enforcement and public safety organizations, which are not authorized to received classified material, warning of terrorist threats |
| RESTRICTED | No longer used by the U.S. but in NATO practice, for national security information that might do slight damge if released |
| CONFIDENTIAL | Capable of doing some harm, such as the ballistics of a specific gun, which would become obvious in battle |
| SECRET | Expected to cause serious damage if leaked; probably the most common level |
| TOP SECRET | If disclosed, would be likely to cause critical damage. Material at this level, besides such things as immediate military plans, often falls into the next level |
| TOP SECRET-CODEWORD | TOP SECRET with additional restrictions for issues such as intelligence sources and menthods, detailed design of nuclear weapons, etc. |
Supplementary classification
For certain kinds of data, there may be a supplemental system that either is considered parallel to or additive with the general classification system. See compartmented control system for practices in the U.S., which are fairly closely reflected in the systems of Australia, Canada, New Zealand, and the United Kingdom. Such material may also receive special and limited handling in NATO and other alliance.
Controversies
Classification is sometimes improperly used to conceal embarrassing information whose disclosure might hurt politically, but not damage the true security.