Security clearance

Definitions

A security clearance is

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a status granted to individuals allowing them access to classified information, i.e., state secrets, or to restricted areas.

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[a]n administrative determination by certain Federal agencies (other than DOE and NRC) that an individual is eligible for access to classified information. Security clearances are designated as Top Secret, Secret, or Confidential, indicating that the recipient is approved for access to National Security Information or Formerly Restricted Data at a classification level equal to or less than his/her security clearance level.

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Overview

Security clearances are required for access to national security information, which may be classified at one of three levels: confidential, secret, and top secret.

The level of classification denotes the degree of protection required for information and the amount of damage that unauthorized disclosure could reasonably be expected to cause to national security. Unauthorized disclosure could reasonably be expected to cause (1) "damage," in the case of confidential information; (2) "serious damage," in the case of secret information; and (3) "exceptionally grave damage," in the case of top secret information.

U.S. military

"Within DoD, a security clearance is a determination that a person is eligible under DoD policy for access to classified information. Clearances allow personnel to access classified information categorized into three levels: top secret, secret, and confidential. The damage to national defense and foreign relations that unauthorized disclosure could reasonably be expected to cause ranges from 'exceptionally grave damage' for top secret information to 'damage' for confidential information."