A method and apparatus for detecting data modification in a layered operating system is disclosed. The apparatus and method provide means to illuminate different areas of a sample at different angles of incidence and detect the angular variation of radiation emitted from the sample in response to the illumination. A search module searches the information residing in the indexed information to obtain a search result. The switching device may further include one or more forward diodes coupled between the gate terminal and the body terminal to bias the body terminal during the on state, and one or more reverse diodes coupled between the gate terminal and the body terminal to bias the body terminal during the off state.