Mobile ad-hoc and sensor networks play an important role in several application fields. The usage of wireless links and the node mobility make the networks prone to security attacks; among these, jamming attacks are insidious and they consist of one or more nodes continuously transmitting dummy packets to keep some wireless links busy. The goal is to destroy the network connectivity or highly reduce its throughput. In this paper we propose a probabilistic formal method, based on a process algebraic approach, targeted at the analysis of connectivity and the evaluation of interference in mobile networks. We show our framework at work on the analysis of an indoor wireless communication scenario. We evaluate the vulnerability of a network to jamming and casual interception with two different routing strategies for the Hybrid Wireless Mesh Protocol (HWMP).