Mobility changes anonymity: new passive threats in mobile ad hoc networks

Privacy in mobile ad hoc networks has new semantics in addition to the conventional notions for infrastructure networks. Mobility enabled by wireless communication has significantly changed privacy issues and anonymity research in many ways. In particular, mobility requires ad hoc routing schemes to transmit messages frequently in an open wireless medium. The routing traffic facilitates adversaries in conducting various attacks threatening the network security and privacy. In this work, we focus on passive routing attacks. We present an extensive study on new anonymity threats and classify the corresponding security demands into three new categories: (1) venue anonymity, (2) privacy of ad hoc network topology, and (3) privacy of motion pattern. These new aspects are all introduced by mobility and left unaddressed in fixed infrastructure. This leads us to investigate new design principles. Our study suggests that on-demand routing, identity-free routing and neighborhood traffic mixing are better design choices to defend against the new anonymity threats in mobile networks. The paper also demonstrates through examples on the visualization of the mobile anonymity attacks and on the quantification of the effectiveness of the attacks.