Named Data Networking (NDN) is one of the most promising information-centric networking architectures that can improve the network performance by supporting the large scale content distribution. However, the use of in-network caching mechanism increases the opportunity of cache pollution attack, where the attackers intend to reduce the cache hit of legal users by releasing fake requests to fill the precious cache with non-popular contents. To prevent the degradation of network performance caused by such an attack, it is becoming particularly important to detect the attack and then throttle it. In this article, we propose a detection and defense scheme with the help of grey forecast, which can effectively exploit the regularity of past Interests and popularity by comprehensively considering three major factors to predict the future popularity of each cached content. If the predicted popularity of any content differs too much from the actually calculated one in several consecutive slices, the pollution attack will be determined. Once the attack is detected, the defense will be taken by suppressing the popularity increase of the suspicious content to mitigate the damage of the pollution attack. We also consider a special case, where there exists a sudden burst of traffic from legal users that cannot be simply dropped. The simulations in ndnSIM indicate that our proposed method is effective in detecting and defending the pollution attack with higher cache hit, higher detecting ratio, and lower hop count compared to other state-of-the-art schemes.

It is very difficult to establish and maintain end-to-end connections in a vehicle ad hoc network (VANET) as a result of high vehicle speed, long inter-vehicle distance, and varying vehicle density. Instead, a store-and-forward strategy has been considered for vehicle communications. The success of this strategy, however, depends heavily on the cooperation among nodes. Different from exiting store-and-forward solutions, we propose predictive routing based on the hidden Markov model (PRHMM) for VANETS, which exploits the regularity of vehicle moving behaviors to increase the transmission performance. As vehicle movements often exhibit a high degree of repetition, including regular visits to certain places and regular contacts during daily activities, we can predict a vehicle's future locations based on the knowledge of past traces and the hidden Markov model. Consequently, the short-term route of a vehicle and its packet delivery probability for a specific mobile destination can be predicted. Moreover, PRHMM enables seamless handoff between vehicle-to-vehicle and vehicle-to-infrastructure communications so that the transmission performance will not be constrained by the vehicle density and moving speed. Simulation evaluation demonstrates that PRHMM performs much better in terms of delivery ratio, end-to-end delay, traffic overhead, and buffer occupancy.