A security guard (also known as a security officer or protective agent) is a person employed by a public or private party to protect the employing party's assets (property, people, equipment, money, etc.) from a variety of hazards (such as waste, damaged property, unsafe worker behavior, criminal activity such as theft, etc.) by using preventative measures. Security guards do this by maintaining a high-visibility presence to deter illegal and inappropriate actions, looking (either directly, through patrols, or indirectly, by monitoring alarm systems or video surveillance cameras) for signs of crime or other hazards (such as a fire), taking action to minimize damage (such as warning and escorting trespassers off property), and reporting any incidents to their clients and emergency services (such as the police or paramedics), as appropriate.
Security officers are generally uniformed to represent their lawful authority to protect private property. Security officers are hired by a range of organizations, including businesses, government departments and agencies and not-for-profit organizations (e.g., churches and charitable organizations).