Wireless Sensor Networks (WSN) support data collection and distributed data processing by means of very small sensing devices that are easy to tamper and cloning: therefore classical security solutions based on access control and strong authentication are difficult to deploy. In this paper we look at the problem of assessing security of node localization. In particular, we analyze the scenario in which Verifiable Multilateration is used to localize nodes and a malicious node try to masquerade as non-malicious. We resort to non-cooperative game theory and we model this scenario as a two-player game. We analyze the optimal players' strategy and we show that the Verifiable Multilateration is indeed a proper mechanism able to reduce the profitability of fake positions. Our analysis demonstrates that, when the verifiers play a pure strategy, the malicious node can always masquerade as unknown with a probability of one and the induced deception could be not negligible. Instead, when the verifiers play mixed strategies, the malicious node can masquerade as unknown with a very low probability and the expected deception is virtually negligible.