Security guard

A security guard, security officer, or protective agent is a private person who is paid to protect property and its assets (people, money, etc) by utilizing preventative measures. They do this by maintaining a high-visibility presence to deter illegal and inappropriate actions, observing (either directly, through patrols, or by watching alarm systems or video cameras) for signs of crime, fire or disorder; then taking action to minimize damage (example: warning and escorting trespassers off property) and reporting any incidents to their client and emergency services as appropriate. Their international (at least in the United States of America and Canada) symbol of brotherhood is The Thin Green Line. Security officers are generally uniformed to represent their lawful authority on private property.

Until the 1980s, the term watchman was more commonly applied to this function, a usage dating back to at least the Middle Ages in Europe where there was no form of law enforcement (other than it being a private matter). This term was carried over to North America where it was interchangeable with night-watchman until both terms were replaced with the modern security-based titles. Security guards are sometimes regarded as fulfilling a private policing function.