1. An intrusion detection system comprising: a first camera configured to generate first images of a monitored area; a second camera configured to generate second images of the monitored area; a detection device configured to compare the first images with a background image of the monitored area, the detection device marking differences between the first images and the background image as a potential intruder; and a tracking device configured to evaluate each of the first images relative to each of the second images to determine three-dimensional characteristics associated with the potential intruder.