This is a list of security clearance terms used in the United States of America. Security clearance levels are used to control access to information that should not be freely available to all. These levels often appear in employment postings for Defense related jobs and other jobs involving substantial amounts of responsibility, such as air traffic control or nuclear energy positions. The different organizations in the United States Federal Government use different terminology and lettering as discussed below. Security clearances can be issued by many United States of America government agencies. The checks for clearances and the granting of clearances is carried out by the US Office of Personnel Management. Use Security clearance levels often appear in employment postings for Defense related jobs, and other jobs involving substantial amounts of responsibility, such as air traffic control or nuclear energy positions. Employers generally prefer to hire people who are already cleared to access classified information at the level needed for a given job or contract, because security clearances can take up to a year to obtain. In general, most employers look for candidates who hold an active Department of Defense (DoD) collateral clearance or a blanket TS/SCI-cleared (Top Secret / Sensitive Compartmented Information) and who have a counterintelligence (CI), full-scope polygraph (FSP), also known as expanded scope screening (ESS). Security levels Security clearances can be issued by many United States of America government agencies, including the Department of Defense (DoD), the Department of State (DOS), the Department of Homeland Security (DHS), the Department of Energy (DoE), the Department of Justice (DoJ), the National Security Agency (NSA), and the Central Intelligence Agency (CIA). DoD issues more than 80% of all clearances. There are three levels of DoD security clearances: TOP SECRET – Will be applied to information in which the unauthorized disclosure could reasonably be expected to cause exceptionally grave damage to the national security. SECRET – Will be applied to information in which the unauthorized disclosure could reasonably be expected to cause serious damage to the national security. CONFIDENTIAL – Will be applied to information in which the unauthorized disclosure could reasonably be expected to cause damage to the national security. USAP: Unacknowledged SAP & "Waived USAP" - Made known only to authorized persons, including members of the appropriate committees of the US Congress. Waived USAP is a subset of USAP. ACCM: Alternative or Compensatory Control Measures - Security measures used