The application discloses a buffer device and a method for controlling data access to an internal memory. The buffer device has a central buffer module coupled to a memory interface to receive a command/address signal via a command/address channel. The central buffer module is configured to detect whether a destination address of the received command/address signal is within a predefined address space, and generate a security read/write signal when the command/address signal is within the predefined address space. The buffer device further has a data buffer module coupled between the memory interface and a memory module to buffer data therebetween. The data buffer module is configured to store reference data, compare the buffered data with the reference data in response to the security read/write signal, and determine whether or not to restrict exchange of the buffered data between the memory module and the memory interface.