One or more video frames may be obtained, and a background model may be constructed based on a first parameter. A second background model may be constructed using the one or more video frames based on a second parameter, the second parameter being different from the first parameter. A difference between the first and second background models may be determined. One or more stationary targets may be determined based on the determined difference. The one or more stationary targets may be classified. An alert concerning the one or more classified stationary targets may be generated.