The technology between face detection and face recognition differs widely, one can compare them to the difference between a small back yard and Lake Victoria. Even though face detection still uses an advance algorithm to captures faces, it cannot hold a candle to face recognition. Though TV shows and films have been perpetrating this myth, where government agencies can access any surveillance system in an area and run the crowds faces, detect, search and compare it within a vast database. This technology might be true and available to many states sponsored agencies around the world but it is not as clearly defined as in film.
Face detection only works by capturing an image of a person walking through a well-positioned area and camera. It then store those faces in a searchable database. Face recognition works by gathering the stored images and comparing it against known faces in a database. As you can see, this is a two-step process. A standalone system does not have the processing power required to handle both face detection and recognition at the same time.
Now, face detection is becoming more common with some DVR or NVR system cameras. As the cameras’ resolutions and pixel densities improve, more devices are coming with face detection and other IVS features. Standalone DVRs and NVRs will not have face recognition built-in to the core system, as this technology is still many generation away.
As far as taking control of a security system by everyday people, this is a plausible theory but not as easy as it is portrayed in Hollywood. Many surveillance systems available on the market do not come with face detection built-in. This means no way of accessing the stored images. Even if a legitimate government agency was able to have access to the said system, one would still require a present warranty (why it is important to change your default login credentials). That is why many police agencies still ask the owners of the security system permission to copy videos before escalating further with a court order.