1. A computer-implemented method for processing one or more video frames, comprising: obtaining, by a computer, one or more video frames; constructing, by the computer, a first background model using the one or more video frames based on a first parameter; constructing, by the computer, a second background model using the one or more video frames based on a second parameter, the second parameter being different from the first parameter; determining, by the computer, a difference between the first and second background models; determining, by the computer, one or more stationary targets based on the determined difference; classifying, by the computer, the one or more stationary targets to obtain one or more classified stationary targets; and generating, by the computer, one or more alerts concerning the one or more classified stationary targets.