1. A method for analyzing video data in a security system, the method comprising: comparing a background model to at least one frame of the video data to identify at least one patch of changed pixels between the background model and the at least one frame; performing morphological image processing on the at least one patch of changed pixels including erosions and/or dilations to generate masks; extracting edge pixels in the background model and the at least one frame with an edge detection algorithm; summing gradient magnitudes for the edge pixels in the background model with respect to the masks; summing gradient magnitudes for edge pixels in the at least one frame of video data with respect to the masks; and characterizing objects in the video data as abandoned or removed based on a comparison of the sums of gradient magnitudes between the background model and the at least one frame.