Exploring a Service-Based Normal Behaviour Profiling System for Botnet Detection

Effective detection of botnet traffic becomes difficult as the attackers use encrypted payload and dynamically changing port numbers (protocols) to bypass signature based detection and deep packet inspection. In this paper, we build a normal profiling-based botnet detection system using three unsupervised learning algorithms on service-based flow-based data, including self-organizing map, local outlier, and k-NN outlier factors. Evaluations on publicly available botnet data sets show that the proposed system could reach up to 91% detection rate with a false alarm rate of 5%

A Novel Multiblock Copolymer of CO₂‑Based PPC-<i>mb</i>-PBS: From Simulation to Experiment

A kind of new biodegradable materials with high performance in a wide range of temperatures was effectively developed via the combination of theoretical calculations and experimental works. The new polymer of poly­(propylene carbonate)-multiblock-poly­(butylene succinate) (PPC-<i>mb</i>-PBS) was designed and synthesized from poly­(propylene carbonate) (PPC) and poly­(butylene succinate) (PBS) segments. The simulation was successfully performed based on their multiblock topology structure. On the basis of the calculation, the <i>T</i>_g of PPC-<i>mb</i>-PBS calculated by molecular dynamics (MD) simulation ranges from −42 to −38 °C that is independent of the block size of PPC segments. The end-to-end distance and mean square displacement (MSD) calculations indicate an inversion behavior of the PPC and PBS between hard and soft segments at different temperatures. The stress–strain behavior of PPC-<i>mb</i>-PBS was also calculated by the MD simulation of uniaxial deformation. The simulated stress of PPC-<i>mb</i>-PBS copolyesters is higher than that of pure PPC under uniaxial extension with the same strain and is found to increase with decreasing PPC block size. To verify the validity of the simulation, the PPC-<i>mb</i>-PBS multiblock copolyesters with various designed block length were synthesized and characterized by ¹H NMR, DOSY, and GPC. Meantime, their thermal and mechanical properties were determined, respectively, by DSC and tensile testing. The measured <i>T</i>_g data and the variation tendency of tensile strength are in very good agreement with the simulated results, demonstrating the ability of the fully atomic-scale MD simulations to well predict the mechanical properties of the synthesized biodegradable polymers