Passive surveillance refers to the monitoring of individuals or groups without their active participation or awareness. This method often involves the collection of data through various means, such as cameras, sensors, or digital tracking, without directly engaging with the subjects being observed. It is commonly used in public spaces to enhance security and gather information. This type of surveillance can also be applied in fields like public health and environmental monitoring, where data is collected to analyze trends or detect issues over time. While passive surveillance can provide valuable insights, it raises concerns about privacy and the ethical implications of monitoring without consent.