How do outdoor security cameras provide night vision?

Night vision on outdoor security cameras is provided by passive infrared (PIR) sensors which measure infrared light radiating from objects in its field of view (Source: Wikipedia).

On an outdoor security camera, infrared LED bulbs are located concentrically around the camera lens to detect this infrared radiation (in the form of heat transfer). The number of infrared LEDs used in a camera help determine its range for night vision.