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. See the National Industrial Security Program Operating Manual for United States examples of safeguarding measures.

There are literally dozens of U.S. government markings that technically are not security classifications, but fall into categories such as "sensitive but unclassified." Some of these markings are used to share information with state and local government, which are not subject to the national-level security system; if certain material, such as terrorism-related material, stayed within the federal government, it would probably carry a security classification. Do not expect the system to be consistent.

See compartmented control system for a discussion of additional restrictions, not always strictly "classifications", that are used for the most sensitive national security information.

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.

Collateral information

Collateral information has a security classification, but no supplementary restrictions. For example, rules of engagement are usually classified SECRET, but have no additional restrictions. These are considered collateral information.

In contrast, the operations manual for a piece of communications intelligence equipment might have the additional restriction CCO, which stands for "handle through communications intelligence channels only." That manual might be SECRET, not collateral SECRET as with the rules of engagement, but compartmented SECRET/CCO.

Markings

Without going into excruciating detail, and freely mentioning that the roles are often broken, some basics of how U.S. and allied documents tend to be market is useful to understand; even a general reader might see a reproduction of a declassified document and might wonder about the notations.

In general text, the security classifications themselves, such as CONFIDENTIAL, are written in all caps. One of the reasons for doing so is that "confidential" and "secret" are words that can occur in ordinary English, so capitalizing a specialized usage disambiguates it from other usage. Another reason, much like a headline, is to draw attention:

• Large bold statements at the top and bottom of each page have an obvious impact
• More often than not, when a security classification is written out in full, the text surrounding it will deal with rules for using that classification in a particular context. The description needs to be unambiguous.

Other, more detailed markings, are very useful when reading a historical document. A title, for example, should reflect any classification of the title itself, as well as the classification of the material under the title. For example, for many years, the very existence of the National Reconnaissance Office was classified SECRET, and any description of its responsibility, started out at TOP SECRET and into compartmented control systems beyond that. A basic description of the agency, sent to would have on its title page,

(S)National Reconnaissance Office General Description (TS)

In principle, but not always practice, each paragraph and figure of a classified document is marked with the classification of the material in that piece of text. A chapter would bear the highest classification found at any place in that chapter. This is very useful in controlling the unneeded propagation of classified material, since a substantial amount of text in many classified documents is unclassified and could be released, but if there is no way for an authorized user to know which specific material is classified, the user cannot know what can be released. Even worse, consider the example of an authorized user is referencing a (hypotheticall) document, classified SECRET, in a new document. The new document has no new classified information in it. Under the principle of "derivative classification", material classified in one document must have the same protection if it is used in another document. The reader does not know paragraph by paragraph classification of the references, so has to assume everything is SECRET. It might turn out that the single paragraph from the original document actually contains to classified information, so the new document is, in good faith, classified SECRET although it contains absolutely no information that cannot be made freely available!

Protection

Classified material must itself have physical protection, and people who are authorized access to it must be checked for trustworthiness. U.S. classified material cannot be transmitted by electronic means that lack encryption. For example, the U.S. SIPRNET network provides Internet Protocol transmission for material up to and including SECRET. Telephones that provide encryption are needed to discuss classified material.

Security clearance

Individuals are granted the privilege of access to a given level of classified material after an investigation and adjudication process variously called an background investigation or positive vetting. The possession of the clearance, however, rarely conveys the right to see all information of that classification; the principle of need to know applies: a submarine captain will have a high security clearance, but security officials might be alarmed if the captain wanted access to the details of a communications technique used purely by ground special operations personnel. See Principle of Least Privilege.

Controversies

Classification is sometimes improperly used to conceal embarrassing information whose disclosure might hurt politically, but not damage the true security.