1. A system for detecting glass breakage, said system comprising: an image detector for acquiring thermal images of a monitored area including a glass portion; a signal processor for generating a reference image from a thermal image of said monitored area, and comparing acquired thermal images against said reference image; and a memory unit for storing said reference image, wherein one of said acquired thermal images is determined as unchanged with respect to said reference image if differences between said acquired thermal image and said reference image are within a predefined threshold, and determined as changed if differences between said acquired thermal image and said reference image exceed said predefined threshold, a glass breakage alert being issued if said acquired thermal image is determined to be changed.