• National security clearances unlock classified information on a need-to-know basis.security image by Kimberly Reinick from Fotolia.com
  
  A security clearance is a measure of how capable and willing a person is to protect classified United States information, according to the U.S. Department of State. The process of applying for national security clearance can take anywhere from a few months to over a year, according to DC Employment Justice Center. Investigators will comb through both your professional and personal life and talk to friends and family members to determine your reliability, trustworthiness and loyalty to the United States.
  
  

Application

• The application process may begin once an individual has secured a position requiring national security clearance and has completed Standard Form 86, Questionnaire for National Security Positions, according to the U.S. Department of State. The form will ask for information that includes citizenship status, education, employment and medical histories, financial status, drug and alcohol use, and more. After submitting the application, the candidate must have a face-to-face interview with an investigator.
  
  The application, which may not be self-submitted, can only apply for the level of national security clearance required for the current position, according to DC Employment Justice Center. You will also be fingerprinted and required to sign a release, which grants investigators the right to contact people you know, perform a criminal background check and examine your credit records, sexual history and mental health.
  
  

Criminal Record

• Although a criminal record may result in denial of national security clearance, it is not an automatic disqualifier. The administrative officer who grants national security clearances will take into consideration successful rehabilitation, how long ago the crime occurred, if you were under pressure from people no longer in your life and if the offense occurred only once, according to DC Employment Justice Center.
  
  

Non-U.S. Citizens

• United States citizenship is not a requirement for national security clearance. A non-U.S. citizen may be granted clearance if he has an expertise useful to the country. Noncitizens are required to undergo a more thorough background check. If clearance is granted, it will be with limited access to classified information, according to DC Employment Justice Center.
  
  

Denial

• Although administrative officers are required to look at the applicant as a whole person, past or present events that qualify you as unreliable, dishonest or disloyal to the country will raise red flags, according to DC Employment Justice Center. A history of disregarding rules and regulations or past actions that indicate a possibility of succumbing to blackmail will also flag your application for potential denial.
  
  Lying to investigators, attempting to conceal information or failing to provide required information will result in automatic denial of national security clearance.