All About Department of Defense Security Clearances

Different jobs require different levels of security

Image shows the desk of a decorated army veteran, featuring a framed flag, a miniature flag, various medals, and three folders. These folders say "confidential", "secret", and "top secret"

Image by Maritsa Patrinos © The Balance 2019

A security clearance investigation ensures that you are eligible for access to national security information. The investigation focuses on your character and conduct, emphasizing such factors as honesty, trustworthiness, reliability, financial responsibility, criminal activity, emotional stability, and other pertinent areas. All investigations consist of checks of national records and credit checks; some investigations also include interviews with individuals who know the candidate for the clearance as well as the candidate himself/herself.

Types of Security Clearances

In the military, all classified information is divided into one of three categories:

  • Confidential: Unauthorized disclosure could cause damage to national security.
  • Secret: Unauthorized disclosure could cause serious damage to national security.
  • Top Secret: Unauthorized disclosure could cause exceptionally grave damage to national security.

In addition to the above, some classified information is so sensitive that even the extra protection measures applied to Top Secret information are not sufficient. This information is known as Sensitive Compartmented Information (SCI) or Special Access Programs (SAP), and one needs special SCI Access or SAP approval to be given access to this information.

You may need one of these levels of security clearance to hold different jobs in the military and with civilian contractors. You can apply for these jobs if you don't have a clearance, but they will give preference to those who already have a security clearance.

The government pays the cost of clearances for military personnel and civilian government employees. But the law requires that contractors pay most of the costs of obtaining clearances for their employees. That's why contractors often advertise for applicants who already hold a valid clearance. Additionally, it saves them time, as they don't have to wait for months for the new employee to obtain a clearance, and begin to do the job they were hired for.

What Determines a Security Clearance Level

For military personnel, two things determine the level of security clearance required: your job and your assignment. Many military jobs require access to classified information, regardless of where you are assigned. In other cases, the job itself may not require a security clearance, but the particular location or unit that the person is assigned to would require giving access to classified information and material. 

The Department of Defense (DOD) operates its security program separate from other government agencies, with its own procedures and standards. A Top Secret Clearance with the Department of Energy, for example, would not necessarily transfer to DoD.

Merely having a certain level of security clearance does not mean you are authorized to view classified information. To have access to classified information, you must possess the necessary two elements: A level of security clearance, at least equal to the classification of the information, and an appropriate "need to know" the information in order to perform your duties.

Just because you have a secret clearance, doesn't mean you would have access to all secret information in the military. You would need to have a specific reason to know that information before you were granted access.

Security Clearance Background Investigations

Security clearance background investigations for the Department of Defense are conducted by the Defense Security Service (DSS). This includes background investigations for military personnel, civilian personnel who work for DoD, and military contractors. The Office of Personnel Management (OPM) conducts security clearance investigations for most other branches of the federal government.

Once it is determined that a military member requires a security clearance because of assignment or job, they complete a Security Clearance Background Investigation Questionnaire. For confidential and secret clearances, applicants have to provide five years' of information; for top secret clearances 10 years of information is required.

The form contains a statement which you sign authorizing the release of any information about you to security clearance investigators. That includes sealed records, juvenile records, expunged records and medical records.

Your clearance could be denied if you conceal information. Once granted, your clearance could be revoked if the military later discovers you lied when filling out the forms.

If you realize after you submit the form that you made a mistake or omitted something important, tell your Security Officer, Recruiter, MEPS Security Interviewer, or the DSS Investigator when you are interviewed. If you do not do so, the error or omission could be held against you during the adjudicative process.

Processing a Clearance Application

Once you complete the questionnaire, it is sent to the Defense Security Service (DSS). They verify the information and perform the actual background investigation. The level of the investigation depends upon the level of access to be granted.

For confidential and secret clearances, they will do a National Agency Check (NAC), which is a search of records held by federal agencies including the FBI and OPM, a Local Agency Check and a review of criminal history records, and a financial check of your credit record.

For a top secret clearance, a Single Scope Background Investigation (SSBI) is performed which includes all of the above, plus field interviews of references, checks of records held by employers, courts, and rental offices. You'll also be subject to an interview with an investigator.

Field Interviews with References

Investigators will do field interviews with the references you listed on the questionnaire and use them to develop more references to interview. Your references will be asked questions about your character and whether you should be given access to classified information or assigned to a sensitive position.

The interviews are wide-ranging with questions about your activities, job history, education, family, finances, drugs, alcohol problems and any police encounters.

Approval or Disapproval of Security Clearance

  • Each military service has its own adjudicator that receives the information from DSS and decides whether to grant the security clearance. They apply their specific guidelines to your case. They may request further investigation of problem areas. Adjudicators are not the final authority. All denials of clearances must be personally reviewed by a branch chief or higher authority.

The investigations are wide-ranging but the following are grounds for denying a security clearance:

  • Conviction of a crime in any U.S. court with a sentence of a year or more in prison
  • Using a controlled substance (as defined in section 102 or the Controlled Substances Act
  • Mental incompetence as determined by a mental health professional approved by the DoD
  • A dishonorable discharge from the military

In general, expect a confidential or secret clearance process to take between one and three months. A top secret will probably take between four and eight months but can take more than a year.

A periodic reinvestigation (PR) is required every five years for a top secret clearance, 10 years for a secret clearance, and 15 years for a confidential clearance. But you may be subject to a random reinvestigation at any time.

When a security clearance is inactivated (ie, when someone gets out of the military, or quits from their government civilian job or contractor job), it can be reactivated within 24 months, as long as the last background investigation falls within the above time frame.

Having a security clearance can give you hiring preference with DoD contractors once you leave the military, as it saves them the expense of conducting one. Once your clearance expires, you will have to have present or pending duties to get it renewed.