Sentence:  No one should be under any illusions about the objective of the Communist Party leadership: it's long-term, systematic <WSD>infiltration</WSD> of social organisations, media and government. By the time China's <WSD>infiltration</WSD> of Australia is readily apparent, it will be too late. 
Meaning of the word marked with <WSD> tags:  The act of secretly entering a physical location and/or organization.