While security guards in other nations may be able to carry guns, it is against the law for private security guards in Australia to do so, especially as Australia has tight gun control regulations.
However, security officers are allowed to physically detain members of the public if required, for example, if they pose a threat to themselves or others or if they are being investigated for a crime. According to Australian law, this extends to all members of the public, not only security personnel. If required, security personnel have the authority to hold individuals until the police arrive at the scene.