# Security clearance

A security clearance is a status granted to individuals allowing them access to classified information (state or organizational secrets) or to restricted areas, after completion of a thorough background check. The term "security clearance" is also sometimes used in private organizations that have a formal process to vet employees for access to sensitive information. A clearance by itself is normally not sufficient to gain access; the organization must also determine that the cleared individual needs to know specific information. No individual is supposed to be granted automatic access to classified information solely because of rank, position, or a security clearance.

## United Kingdom
### National Security Clearance types

National Security Clearances are a hierarchy of levels, depending on the classification of materials that can be accessed—Baseline Personnel Security Standard (BPSS), Counter-Terrorist Check (CTC), Enhanced Baseline Standard (EBS), Security Check (SC), enhanced Security Check (eSC), Developed Vetting (DV), enhanced Developed Vetting (eDV), and STRAP.
The BPSS is the entry-level National Security Clearance, and both CTC and EBS are effectively enhancements to the BPSS, with CTC relating to checking for susceptibility to extremist persuasion, and EBS relating to checking for susceptibility to espionage persuasion, the latter being needed for supervised access to SECRET material. The SC again is focused on susceptibility to espionage persuasion, and is required for an individual to have long-term unsupervised access to SECRET material and occasional access to TOP SECRET (TS) material, whilst for regular access to TS the DV, eDV is required. Occasionally STRAP is required with DV.
Those with National Security Clearance are commonly required to sign a statement to the effect that they agree to abide by the restrictions of the Official Secrets Act (OSA). This is popularly referred to as "signing the Official Secrets Act". Signing this has no effect on which actions are legal, as the act is a law, not a contract, and individuals are bound by it whether or not they have signed it. Signing it is intended more as a reminder to the person that they are under such obligations. To this end, it is common to sign this statement both before and after a period of employment that involves access to secrets.

### National Security Clearance history

After the United States entered into World War II, Britain changed its security classifications to match those of the U.S.. Previously, classifications had included the top classification "Most Secret", but it soon became apparent that the United States did not fully understand the UK's classifications, and classified information appeared in the U.S.'s press. This spearheaded the uniformity in classification between the United Kingdom and the United States. The terminology and levels of British security classifications have also changed from Positive Vetting and Enhanced Positive Vetting to SC, eSC, DV, eDV and STRAP.

### Other UK clearances

In addition to National Security Clearances, other types of roles and organisations stipulate a need for clearances, including:
* Vulnerable Group Access (including children), as operated by the Disclosure and Barring Service (DBS), replacing former Criminal Records Bureau (CRB) and Independent Safeguarding Authority (ISA) checks
* Law Enforcement, with a hierarchy of Police Personnel Vetting (PPV) and Non-Police Personnel Vetting (NPPV) levels.

## United States

A United States security clearance is an official determination that an individual may access information classified by the United States Government. Security clearances are hierarchical; each level grants the holder access to information in that level and the levels below it.

## United Nations

The UN has a Security Clearance (SC) procedure and document for United Nations staff travelling to areas designated as security phase areas, with numbers ranging from one to five ("no-phase" areas are calm countries where no SC is required).
United Nations staff can apply for SC online, at the website of the Department for Safety and Security.

## Individuals who have had security clearances revoked

In the post World War II era, there have been several highly publicized, and often controversial, cases of officials or scientists having their security clearances revoked, including:
| Name | Reason | Year of revocation |
| Sandy Berger | Mishandling of classified documents | 2005 |
| Rod Blagojevich | Corruption charges | 2008 |
| John O. Brennan | Claimed but not processed | N/A |
| John M. Deutch | Mishandling of classified information | 1999 |
| Thomas Andrews Drake | Unauthorized disclosure of secrets | 2010 |
| Abdel-Moniem El-Ganayni | Unknown reasons | 2008 |
| Michael T. Flynn | Lying to the FBI | 2017 |
| Wen Ho Lee | Espionage charges | 1999 |
| Robert Oppenheimer | Communist sympathies | 1954 |
| Aldric Saucier | Whistleblowing on fraud | 1992 |
| Edward Snowden | Unauthorized disclosure of secrets | 2013 |
| Alan Turing (UK) | Homosexuality conviction | 1952 |
| Qian Xuesen | Communist sympathies | 1950 |
This list does not cover people whose security clearance lapsed possibly following changing their job.