To prepare for this question, start by listing your strengths. You can narrow them down by thinking about how they help you as a security manager. Think of situations where your strengths help you shine, such as troubleshooting an access control system, or training a new employee. You could give an example of how your problem solving ability has helped you to navigate a variety of issues, listing some of the different software, tools and databases you have worked with. You could also share how you are great at dealing with conflict if it arises, referencing a situation where you used your communication and listening skills to dodge a potential blowout with a staff member. Using examples helps the interviewer get a better picture of your strengths in action.
"My greatest strength is my ability to lead a team and to be a positive influence on them. Every team that I've lead has enjoyed a significant increase in productivity and efficiency. Whether I was a cadet sergeant in military academy, a project leader in college, or a security supervisor, my team members were more loyal, saw more successes, and learned more, all because I know how to serve and lead. This means that, if I'm hired as a security manager, you're going to enjoy improved performance from the security team."