If you work for a federal agency, you can have your security clearance suspended or revoked by affiliating with or sympathizing with terrorists, associating with foreign citizens of businesses that could lead to a case of coercion, and holding dual citizenship and/or service in a foreign military.

Other reasons for suspension or revocation, not just at the federal level, include engaging in outside activities that involve dissecting or disseminating materials relating to protected technology or other closely guarded secrets.

Criminal conduct is a universal reason for losing security clearance, as are security violations, misuse of information technology, sexual assault, alcohol or drug consumption, and psychological conditions.

Personal conduct, including associating with known criminals and engaging in unsavory behavior are other reasons you might be denied security clearance.