Information and Communication technology is nowadays undeniably the fundamental pillar of any company seeking a high level of effectiveness, and reactivity. In fact, communication technologies made it possible to improve productivity, and have constrained the companies to adapt their working methods to survive to market competition. However, one cannot ignore the existence of intrinsic and extrinsic vulnerabilities of these communication systems, which confers on networks security fundamental role. Even if networks have evolved from wired to wireless networks, network security objectives remained the same for both; to preserve integrity, confidentiality and availability of information and networks resources. Several mechanisms have been developed to achieve these goals. For instance, we can mention authentication, encryption, access control. According to the network environment, certain security mechanisms are not mature enough due to the youth of certain network technologies such as wireless, ad hoc or sensor networks. However, even with the maturity, and even if they are already largely implemented in the market network security products, like firewalls and VPNs, certain mechanisms still need improvements. It is also important to consider resource limitations of mobile terminals and radio-communications in order to adapt security mechanisms of wired networks to wireless networks' context. We attend a major evolution of networks that could be summarized by the need to allow the user to communicate in any place statically or while moving. This was possible thanks to the evolution of wireless and mobile networks, and the evolution of mobile terminals' design. Even if security solutions are not yet finalized in those environments, the deployment of wireless networks is already effective and will tend to be deployed even more because of the increasing need of user's mobility, flexibility and services. In order to achieve this challenge, industrial and academic research groups are working on one hand developing wireless and mobile technologies, with or without infrastructure, offering more and more resources and security, and on the other hand, developing autonomous terminals increasingly powerful (PDA, telephones). This workshop (MWNS 2008) is a first initiative to gather security researchers in both wireless and mobile networks so that they can present their latest research results in this field and provide good discussion about the existing security issues and challenges in this resource limited and easy spying networks; the wireless and mobile networks.