A security officer (or security guard) is a person who is paid to protect property, assets, or people. They are usually privately and formally employed civilian personnel. Security officers are generally uniformed and act to protect property 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 and reporting any incidents to their client and emergency services as appropriate.

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Many security firms and proprietary security departments practice the “detect, deter, observe and report” methodology. Security officers are not required to make arrests, but have the authority to make a citizen’s arrest, or otherwise act as an agent of law enforcement, for example, at the request of a police officer or sheriff.

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A private security guards primary duty is the prevention and deterrence of crime. Security guard personnel enforce company rules and can act to protect lives and property, and they often have a contractual obligation to provide these actions. In addition to basic deterrence, security officers are often trained to perform specialized tasks such as arrest and control (including handcuffing and restraints), operate emergency equipment, perform first aid, CPR, take accurate notes, write detailed reports, and perform other tasks as required by the client they are serving.