1. An alarm system for protecting a structure, comprising: at least one motion detector arranged to have a field of view external of the structure and including an area proximate the structure; at least one camera associated with each of said at least one motion detector, each of said at least one camera being arranged relative to the associated one of said at least one motion detector such that said camera has a field of view encompassing at least part of the field of view of the associated one of said at least one motion detector, said at least one camera having a dormant state in which images are not obtained and an active state in which images are obtained and being activated into the active state when the associated one of said at least one motion detector detects motion such that said at least one camera obtains an image of the source of the motion detected by the associated one of said at least one motion detector; and a processor coupled to said at least one camera and arranged to receive the image obtained by said at least one camera, derive a silhouette of any objects in the image, compare the silhouettes to a library of stored silhouettes having associated object identification to determine an exact or closest match of the derived silhouette to one of the stored silhouettes and retrieve the object identification associated with the exact or closest match, said processor being arranged to react to the detection of motion by said at least one motion detector based on the object identification.