Current parallel and distributed networks and systems are facing serious threats from network terrorism and crime, which cause huge financial losses and are potentially hazardous to life. In particular, the most serious forms of network attack are large-scale, distributed and coordinated Internet attacks, such as large-scale stealthy scans, worm outbreaks, distributed denial of service attacks and botnets. This special issue focuses on issues related to Network and System Security, such as authentication, access control, availability, integrity, privacy, confidentiality, dependability and sustainability of computer networks and systems and highlights the recent advances in this area. There were 45 paper submissions for this special issue and each paper went through a rigorous peer-review process. The papers were sent to three to five referees and most have gone through at least two rounds of reviews. To avoid potential conflict of interest, the Editor-in-Chief exclusively handled papers involving any guest editor as an author. Finally, five papers were selected and the 11% acceptance rate reflects the high standard of quality control. The papers that are being published here represent advances in the fields of sensor network key management, sensor network data authentication, host-based intrusion detection and user privacy protection. Tian et al.[1] provide a comprehensive survey of self-healing key distribution schemes for wireless networks. A classification of self-healing key distribution is proposed and open problems are discussed, which is helpful for future research. Oliverira et al.[2] develop a security solution, namely Secure-TWS, for efficient authentication of data sent by a resource-constrained sensor node to multiple users using digital signatures. It provides evaluation of resource overheads in communication and computation for three suitable signatures—the Elliptic Curve Digital Signature Algorithm, the Boneh–Lynn–Shacham and the Boneh–Boyen short signature schemes. Tupakula and Varadharajan [3] design an intrusion detection system for virtual machine-based systems. The paper proposes a novel security architecture using a virtual machine monitor-based intrusion detection system called VICTOR, which takes into account the specific characteristics of an operating system and applications running in each virtual machine at a fine granular level to detect attacks. Yu et al.[4] investigate how to attack anonymous web browsing at local area networks through browsing dynamics. A hidden Markov model has been used to model the browsing dynamics for the website. Extensive experiments demonstrate that the attack accuracy can be more than 80%. Several counter attack strategies are discussed. Sun et al.[5] study the problem of protecting the privacy of individuals in large public rating data and propose a novel anonymity model to protect privacy in large survey rating data. Experiments on real-life data show that the proposed slicing technique is fast and scalable with data size, and much more efficient in terms of execution time and space overhead than the heuristic pair-wise method.