A security clearance is the process of determining your trustworthiness and reliability before granting you access to national security information. Only the federal government can grant someone a security clearance. To get one, you must work for a government agency or contractor and conduct business that justifies you having access to highly sensitive information. The process begins when your employer or prospective employer submits your paperwork to the investigating/adjudication agency.
Once you have turned in the documentation, the designated agency will begin the security clearance investigation, which may include interviews with family, friends, colleagues and others; a review of your credit, financial, medical and other history; a background check to determine the use of illegal drugs, criminal record and contact with foreign nationals; and a check on many other areas of your life. This process may take several months up to a year depending on backlog, need for more information, depth of the investigation and adjudication process, among other factors.