Special circumstances: it is a non-professional investigation force used in criminal or national security investigation, which can timely reflect some information needed for investigation and the internal information of criminals, so as to facilitate investigators to investigate and solve cases. Special circumstances are generally volunteers, who use their background, relationship, identity and skills to perform assigned tasks, which is somewhat similar to the "informants" of Hong Kong and Taiwan. The name of intelligence officer is relatively broad, some refer to the manager of intelligence information, and some refer to the collector of intelligence.