1. A surveillance system comprising: a foreground detection unit which predicts a foreground pixel based on foreground region information and motion information extracted from a video frame and performs validation on the predicted foreground pixel based on a texture feature so as to extract a foreground binary large object (BLOB); and an event detection unit which classifies the video frame based on the motion information, and determines whether an abnormal event has occurred in a monitoring region, based on results of classifications of a certain number of video frames.