We pay our attention towards secure and robust communication in the presence of a Reconfigurable Intelligent Surface (RIS)-enhanced mobile eavesdropping attacker in Multiple-Input Multiple-Output (MIMO)wireless networks.Specifically,we first provide a unifying framework that generalizes specific intelligent wiretap model wherein the passive eavesdropper configured with any number of antennas is potentially mobile and can actively optimize its received signal strength with the help of RIS by intelligently manipulating wiretap channel characteristics.To effectively mitigate this intractable threat,we then propose a novel and lightweight secure communication scheme from the perspective of information theory.The main idea is that the data processing can in some cases be observed as communication channel,and a random bit-flipping scheme is then carefully involved for the legitimate transmitter to minimize the mutual information between the secret message and the passive eavesdropper's received data.The Singular Value Decomposition (SVD)-based precoding strategy is also implemented to optimize power allocation,and thus ensure that the legitimate receiver is not subject to interference from this random bit-flipping.The corresponding results depict that our secure communication scheme is practically desired, which does not require any a prior knowledge of the eavesdropper's full instantaneous Channel State Information (ICSI). Furthermore,we consider the RIS optimization problem from the eavesdropper's perspective,and provide RIS phase shift design solutions under different attacking scenarios.Finally,the optimal detection schemes respectively for the legitimate user and the eavesdropper are provided,and comprehensive simulations are presented to verify our theoretical analysis and show the effectiveness and robustness of our secure communication scheme across a wide range of attacking scenarios.

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