Moving Target Defense (MTD) has emerged as a newcomer into the asymmetric field of attack and defense, and shuffling-based MTD has been regarded as one of the most effective ways to mitigate DDoS attacks. However, previous work does not acknowledge that frequent shuffles would significantly intensify the overhead. MTD requires a quantitative measure to compare the cost and effectiveness of available adaptations and explore the best trade-off between them. In this paper, therefore, we propose a new costeffective shuffling method against DDoS attacks using MTD. By exploiting Multi-Objective Markov Decision Processes to model the interaction between the attacker and the defender, and designing a cost-effective shuffling algorithm, we study the best trade-off between the effectiveness and cost of shuffling in a given shuffling scenario. Finally, simulation and experimentation on an experimental software defined network (SDN) indicate that our approach imposes an acceptable shuffling overload and is effective in mitigating DDoS attacks.
CCS CONCEPTS• Networks → Denial-of-service attacks; • Security and privacy → Formal security models.
This article introduces a novel transition between coplanar waveguide (CPW) and air-filled rectangular waveguide (RWG). A rectangular radiator etched with a semi-elliptic slot is connected to the center conductor of CPW to realize the transition, which broadens the bandwidth. This direct transition does not require intermediate transition or air-bridges. Moreover, the planar circuit of the transition can be designed with high- and low-permittivity materials (εr = 10.2 and 2.22), which offer more benefits in both PCB and MMIC design. Two back-to-back transition prototypes at X-band are designed, fabricated and measured. The 15 dB fractional bandwidths are expanded to 44.7% and 47.6% respectively, which have been demonstrated in both of the transitions (εr = 10.2 and 2.22). The measurement results agree well with simulation results, which validate the feasibility of this design.
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