An intelligent entrance detection system is provided where, primarily, any authorized or unauthorized entry to an area of a residential (or small industrial) unit covered by a wireless network is automatically detected from active off-the-shelf devices in that area. After the detection, an identification algorithm is employed to verify if this entry is a legal or illegal action. Based on this verification, either the routine smart home system is activated or a hazardous monitoring period begins to further investigate the suspicious event. If the illegal entrance is confirmed during the hazardous monitoring period, the owner of the property is informed through an intruder alarm protocol. In this invention, all of the analytic and processing steps, including entrance detection, owner identification, and device-free authority verification are designed based on monitoring and quantification of changes in surrounding wireless signals originated by human or object movements within the sensing area.