1. A method of classifying an abnormal behavior of a detected object in a video frame, the video frame comprising a plurality of blocks and the detected object being associated with a subset of the plurality of blocks, said method comprising steps of: (a) associating a behavior model with each of the plurality of blocks, wherein each behavior model includes a set of behavior modes having a set of parameters; (b) for each block in the video frame associated with the detected object: (i) determining a set of behavior statistics associated with the detected object in the video frame, based on the detected object and the set of parameters; (ii) comparing the determined set of behavior statistics with each behavior mode in the set of behavior modes associated with that block to determine an abnormality score; and (iii) selecting the lowest abnormality score from the determined abnormality scores; and (c) classifying the abnormal behavior of the detected object based on the lowest abnormality scores associated with the subset of the plurality of blocks associated with the detected object, said classifying step comprising: (i) determining an average abnormality score for all blocks in the subset of blocks associated with the detected object, based on the lowest abnormality scores; (ii) comparing the average abnormality score with an abnormality threshold; and (iii) triggering an abnormality event if the average abnormality score exceeds the abnormality threshold.