DeepC2: AI-powered Covert Botnet Command and Control on OSNs

Botnets are one of the major threats to computer security. In previous botnet command and control (C&C) scenarios using online social networks (OSNs), methods for addressing (e.g., IDs, links, or DGAs) are hardcoded into bots. Once a bot is reverse engineered, the botmaster and C&C infrastructure will be exposed. Additionally, abnormal content from explicit commands may expose botmasters and raise anomalies on OSNs. To overcome these deficiencies, we proposed DeepC2, an AI-powered covert C&C method on OSNs. By leveraging neural networks, bots can find botmasters by avatars, which are converted into feature vectors and embedded into bots. Adversaries cannot infer botmasters' accounts from the vectors. Commands are embedded into normal contents (e.g., tweets and comments) using text data augmentation and hash collision. Experiments on Twitter show that command-embedded contents can be generated efficiently, and bots can find botmasters and obtain commands accurately. Security analysis on different scenarios show that DeepC2 is robust and hard to be shut down. By demonstrating how AI may help promote covert communication on OSNs, this work provides a new perspective on botnet detection and confrontation.Comment: 13 pages, 15 figures, 7 tables. Discussion on possible countermeasures update

Two new species of Perenniporia (Polyporales, Basidiomycota)

Two new species of Perenniporia, P. pseudotephropora sp. nov. and P. subcorticola sp. nov., are introduced respectively from Brazil and China based on morphological characteristics and molecular data. Perenniporia pseudotephropora is characterised by perennial, pileate basidiocarps with distinctly stratified tubes, grey pores, tissues becoming dark in KOH, a dimitic hyphal system with slightly dextrinoid arboriform skeletal hyphae and broadly ellipsoid to subglobose, truncate, weakly dextrinoid, cyanophilous basidiospores, measuring 4.9–5.2 × 4–4.8 μm. Perenniporia subcorticola is characterised by resupinate basidiocarps, yellow pores with thick dissepiments, tissues becoming dark in KOH, flexuous skeletal hyphae, ellipsoid, truncate and slightly dextrinoid basidiospores, measuring 4.2–5 × 3.5–4.2 µm. The morphologically-similar species and phylogenetically closely-related species to the two new species are discussed

Intelligent Diagnosis of Rolling Element Bearing Based on Refined Composite Multiscale Reverse Dispersion Entropy and Random Forest

Rolling bearings are the vital components of large electromechanical equipment, thus it is of great significance to develop intelligent fault diagnoses for them to improve equipment operation reliability. In this paper, a fault diagnosis method based on refined composite multiscale reverse dispersion entropy (RCMRDE) and random forest is developed. Firstly, rolling bearing vibration signals are adaptively decomposed by variational mode decomposition (VMD), and then the RCMRDE values of 25 scales are calculated for original signal and each decomposed component as the initial feature set. Secondly, based on the joint mutual information maximization (JMIM) algorithm, the top 15 sensitive features are selected as a new feature set and feed into random forest model to identify bearing health status. Finally, to verify the effectiveness and superiority of the presented method, actual data acquisition and analysis are performed on the bearing fault diagnosis experimental platform. These results indicate that the presented method can precisely diagnose bearing fault types and damage degree, and the average identification accuracy rate is 97.33%. Compared with the refine composite multiscale dispersion entropy (RCMDE) and multiscale dispersion entropy (MDE), the fault diagnosis accuracy is improved by 2.67% and 8.67%, respectively. Furthermore, compared with the RCMRDE method without VMD decomposition, the fault diagnosis accuracy is improved by 3.67%. Research results prove that a better feature extraction technique is proposed, which can effectively overcome the deficiency of existing entropy and significantly enhance the ability of fault identification

APPLICATION OF THE DUAL TREE COMPLEX WAVELET TRANSFORM AND MINIMUM ENTROPY DECONVOLUTION IN INCIPIENT FAULT DIAGNOSIS OF THE GEAR BOX

Aiming at the problem that early fault characteristic signal of bearing in gear box is weak and affected by the environmental noise seriously,which makes the fault feature information is difficult to identify,a early fault diagnosis method of gear box is proposed based on dual-tree complex wavelet transform and minimum entropy deconvolution. Firstly,the dual-tree complex wavelet transform method was used to decompose the collected vibration signals into several components with different frequency bands.. However,due to the interference of noise,it was difficult to make a correct judgment from the spectrum of the components. Then,the component that contains fault feature was processed by using minimum entropy deconvolution to reduce the strong background noise and enhance the fault information. Finally,the Hilbert envelope spectrum analysis was performed to identify the frequency of the bearing fault. The effectiveness and superiority of the proposed method are verified by Simulation experiment of bearing fault in gear box and engineering application

Two new brown rot polypores from tropical China

Brown-rot fungi are types of fungi that selectively degrade cellulose and hemicellulose from wood and are perhaps the most important agents involved in the degradation of wood products and dead wood in forest ecosystem. Two new brown-rot species, collected from southern China, are nested within the clades of Fomitopsis sensu stricto and Oligoporus sensu stricto, respectively. Their positions are strongly supported in the Maximum Likelihood phylogenetic tree of the concatenated the internal transcribed spacer (ITS) regions, the large subunit of nuclear ribosomal RNA gene (nLSU), the small subunit of nuclear ribosomal RNA gene (nuSSU), the small subunit of mitochondrial rRNA gene (mtSSU), the largest subunit of RNA polymerase II (RPB1), the second largest subunit of RNA polymerase II (RPB2) and the translation elongation factor 1-α gene (TEF1) sequences. Fomitopsis bambusae, only found on bamboo, is characterised by its resupinate to effused-reflexed or pileate basidiocarps, small pores (6–9 per mm), the absence of cystidia, short cylindrical to oblong-ellipsoid basidiospores measuring 4.2–6.1 × 2–2.3 μm. Oligoporus podocarpi is characterised by white to pale cream pore surface, round or sometimes angular pores (5–6 per mm), broadly ellipsoid to reniform basidiospores measuring 3.8–4.2 × 2–2.3 μm and growing on Podocarpus. Illustrated descriptions of these two novel species, Fomitopsis bambusae and Oligoporus podocarpi, are provided

Modeling and Identification Method of Bolt Loosening of Joint Surface under Axial Tension of Multistage Disk-Drum Rotor

Individual bolt at key connection positions is prone to loose when the engine is cycle-operating under complex loads. A joint surface equivalent stiffness model is derived and developed based on the connection characteristics of bolt screwing in the multi-exciting environment of the high-pressure rotor. The model is used to analyse the effect of bolt missing at circumferential positions with the equivalent stiffness loss. Vibration experiments under both axial force and lateral impact were carried out to obtain the dynamic response feature of the multistage disk-drum simulated rotor with missing one bolt at different positions. The Spearman correlation coefficient was applied to evaluate the identification effect of different measuring points on the bolt loosening position. The study shows that the eigenfrequencies of experimental results have a consistent trend with the equivalent stiffness variation caused by single bolt missing model. This method also provides a theoretical basis for the detection of bolt deviation position with multi-exciting vibration detection

Two new species of Perenniporia sensu lato (Polyporales, Basidiomycota) from China and two new combinations in Crassisporus

Phylogenetic and morphological analyses on Perenniporia s.l. were carried out. Phylogenies on Perenniporia s.l. are reconstructed with two loci DNA sequences including the internal transcribed spacer (ITS) regions and the large subunit (nLSU). Two new species from Yunnan Province, southwest China, Perenniporia prunicola and P. rosicola in Perenniporia s.l., are illustrated and described. Perenniporia prunicola is characterised by the perennial and resupinate basidiomata with a clay pink pore surface when fresh, a trimitic hyphal system, the presence of clavate to fusiform hymenial cystidia, ellipsoid to broadly ellipsoid basidiospores measuring 4.8–6.2 × 3.6–4.5 µm. Perenniporia rosicola is characterised by annual and resupinate basidiomata with a white pore surface when fresh, a dimitic hyphal system, the presence of dendrohyphidia, broadly ellipsoid to subglobose basidiospores measuring 5–5.8 × 4–5.2 μm. In addition, Crassisporus is a genus in Perenniporia s.l., in which two new combinations Crassisporus minutus and C. mollissimus are proposed. Main morphological characteristics of species related to new taxa are also provided

Two new species of Perenniporia sensu lato (Polyporales, Basidiomycota) from China and two new combinations in Crassisporus

Phylogenetic and morphological analyses on Perenniporia s.l. were carried out. Phylogenies on Perenniporia s.l. are reconstructed with two loci DNA sequences including the internal transcribed spacer (ITS) regions and the large subunit (nLSU). Two new species from Yunnan Province, southwest China, Perenniporia prunicola and P. rosicola in Perenniporia s.l., are illustrated and described. Perenniporia prunicola is characterised by the perennial and resupinate basidiomata with a clay pink pore surface when fresh, a trimitic hyphal system, the presence of clavate to fusiform hymenial cystidia, ellipsoid to broadly ellipsoid basidiospores measuring 4.8–6.2 × 3.6–4.5 µm. Perenniporia rosicola is characterised by annual and resupinate basidiomata with a white pore surface when fresh, a dimitic hyphal system, the presence of dendrohyphidia, broadly ellipsoid to subglobose basidiospores measuring 5–5.8 × 4–5.2 μm. In addition, Crassisporus is a genus in Perenniporia s.l., in which two new combinations Crassisporus minutus and C. mollissimus are proposed. Main morphological characteristics of species related to new taxa are also provided

Low-Temperature Rapid Synthesis of Rod-Like ZrB₂ Powders by Molten-Salt and Microwave Co-Assisted Carbothermal Reduction

A novel molten-salt and microwave coassisted carbothermal reduction (termed as MSM-CTR) method was developed to prepare ZrB2 powders from raw materials of ZrO2, B4C, and amorphous carbon. The results indicated that the carbothermal reduction reaction for synthesizing ZrB2 was initiated at the temperature as low as 1150⁰C, and phase pure ZrB2 powders were obtained after only 20 min at 1200⁰C, which were significantly milder than that of the conventional CTR method as well as the modified CTR method even using active metal as additional reducing agents. More interestingly, the as-obtained ZrB2 powders consisted of well-defined single-crystalline nanorods, which had diameters of 40–80 nm and high aspect ratios of \u3e10. These results demonstrated that the MSM-CTR is a simple and efficient route for preparation of high-quality ZrB2 powders