Classified information

Classified information is material that a government body claims is sensitive information that requires protection of confidentiality, integrity, or availability. Access is restricted by law or regulation to particular groups of people, and mishandling can incur criminal penalties and loss of respect. A formal security clearance is often required to handle classified documents or access classified data. The clearance process usually requires a satisfactory background investigation. Documents and other information assets are typically marked with one of several (hierarchical) levels of sensitivity—e.g. restricted, confidential, secret and top secret. The choice of level is often based on an impact assessment; governments often have their own set of rules which include the levels, rules on determining the level for an information asset, and rules on how to protect information classified at each level. This often includes security clearances for personnel handling the information. Although "classified information" refers to the formal categorization and marking of material by level of sensitivity, it has also developed a sense synonymous with "censored" in US English. A distinction is often made between formal security classification and privacy markings such as "commercial in confidence". Classifications can be used with additional keywords that give more detailed instructions on how data should be used or protected.

Some corporations and non-government organizations also assign sensitive information to multiple levels of protection, either from a desire to protect trade secrets, or because of laws and regulations governing various matters such as personal privacy, sealed legal proceedings and the timing of financial information releases.

Government classification
The purpose of classification is to protect information. Higher classifications protect information that might endanger national security. Classification formalises what constitutes a "state secret" and accords different levels of protection based on the expected damage the information might cause in the wrong hands.

However, classified information is frequently "leaked" to reporters by officials for political purposes. Several U.S. presidents have leaked sensitive information to get their point across to the public.

Typical classification levels
Although the classification systems vary from country to country, most have levels corresponding to the following British definitions (from the highest level to lowest)

Top secret is the highest level of classified information. Information is further compartmented so that specific access using a code word after top secret is a legal way to hide collective and important information. Such material would cause "exceptionally grave damage" to national security if made publicly available. Prior to 1942, the UK and other members of the British Empire used Most Secret, but this was changed to match the US's Top Secret to simplify Allied interoperability.

The Washington Post reports in an investigation entitled Top secret America, that per 2010 "An estimated 854,000 people ... hold top-secret security clearances" in the United States.

Secret
Secret material would cause "serious damage" to national security if it were publicly available.

In the United States, operational "Secret" information can be marked with an additional "LIMDIS", to limit readership.

Confidential
Confidential material would cause damage or be prejudicial to national security if publicly available.

Restricted
Restricted material would cause "undesirable effects" if publicly available. Some countries do not have such a classification; in public sectors, such as commercial industries, such level are also called and known as "Private Information".

Official
Official material forms the generality of government business, public service delivery and commercial activity. This includes a diverse range of information, of varying sensitivities, and with differing consequences resulting from compromise or loss. OFFICIAL information must be secured against a threat model that is broadly similar to that faced by a large private company.

The OFFICIAL classification replaces the Confidential and Restricted classifications after April 2014 in the UK.

Unclassified
Unclassified is technically not a classification level, but this is a feature of some classification schemes, used for government documents that do not merit a particular classification. This is because the information is low-impact, and therefore does not require any special protection, such as vetting of personnel.

A plethora of pseudo-classifications exist under this category.

Clearance
Clearance is a general classification, that comprises a variety of rules controlling the level of permission required to view so classified information, and how it must be stored, transmitted, and destroyed. Additionally, access is restricted on a "need to know" basis. Simply possessing a clearance does not automatically authorize the individual to view all material classified at that level or below that level. The individual must present a legitimate "need to know" in addition to the proper level of clearance.

Compartmented information
In addition to the general risk-based classification levels, additional compartmented constraints on access exist, such as (in the U.S.) Special Intelligence (SI), which protects intelligence sources and methods, No Foreign dissemination (NOFORN), which restricts dissemination to U.S. nationals, and Originator Controlled dissemination (ORCON), which ensures that the originator can track possessors of the information. Information in these compartments is usually marked with specific keywords in addition to the classification level.

Government information about nuclear weapons often has an additional marking to show it contains such information (CNWDI).

International
When a government agency or group shares information between an agency or group of other country’s government they will generally employ a special classification scheme that both parties have previously agreed to honour.

For example the marking ATOMAL, is applied to U.S. RESTRICTED DATA or FORMERLY RESTRICTED DATA and United Kingdom ATOMIC information that has been released to NATO. ATOMAL information is marked COSMIC TOP SECRET ATOMAL (CTSA), NATO SECRET ATOMAL (NSAT), or NATO CONFIDENTIAL ATOMAL (NCA).

NATO classifications
For example, sensitive information shared amongst NATO allies has four levels of security classification; from most to least classified: A special case exists with regard to NATO UNCLASSIFIED (NU) information. Documents with this marking are NATO property (copyright) and must not be made public without NATO permission. In general documents with this classification aren't cleared for internet-transmission either, unless clearly marked with RELEASABLE FOR INTERNET TRANSMISSION. Documents that can be made public, however, should be clearly marked with NON SENSITIVE INFORMATION RELEASABLE TO THE PUBLIC.
 * 1) COSMIC TOP SECRET (CTS),
 * 2) NATO SECRET (NS),
 * 3) NATO CONFIDENTIAL (NC), and
 * 4) NATO RESTRICTED (NR).

International organisations
TRÈS SECRET UE/EU TOP SECRET: information and material the unauthorised disclosure of which could cause exceptionally grave prejudice to the essential interests of the European Union or of one or more of the Member States; SECRET UE/EU SECRET: information and material the unauthorised disclosure of which could seriously harm the essential interests of the European Union or of one or more of the Member States; CONFIDENTIEL UE/EU CONFIDENTIAL: information and material the unauthorised disclosure of which could harm the essential interests of the European Union or of one or more of the Member States; RESTREINT UE/EU RESTRICTED: information and material the unauthorised disclosure of which could be disadvantageous to the interests of the European Union or of one or more of the Member States.
 * European Commission, has 5 levels, EU TOP SECRET, EU SECRET, EU CONFIDENTIAL, EU RESTRICTED, and EU COUNCIL / COMMISSION. (Note that usually the French term is used.)


 * Organisation for Joint Armament Cooperation, a European defence organisation, has three levels of classification: OCCAR SECRET, OCCAR CONFIDENTIAL, and OCCAR RESTRICTED.
 * ECIPS, the European Centre for Information Policy and Security, has 4 levels of Security Information, COSMIC (TOP SECRET), EC-SECRET, EC-CONFIDENTIAL and EC-COMMITTEE.