Hard-coded backdoor detection method based on semantic conflict

The current router security issues focus on the mining and utilization of memory-type vulnerabilities, but there is low interest in detecting backdoors.Hard-coded backdoor is one of the most common backdoors, which is simple and convenient to set up and can be implemented with only a small amount of code.However, it is difficult to be discovered and often causes serious safety hazard and economic loss.The triggering process of hard-coded backdoor is inseparable from string comparison functions.Therefore, the detection of hard-coded backdoors relies on string comparison functions, which are mainly divided into static analysis method and symbolic execution method.The former has a high degree of automation, but has a high false positive rate and poor detection results.The latter has a high accuracy rate, but cannot automate large-scale detection of firmware, and faces the problem of path explosion or even unable to constrain solution.Aiming at the above problems, a hard-coded backdoor detection algorithm based on string text semantic conflict (Stect) was proposed since static analysis and the think of stain analysis.Stect started from the commonly used string comparison functions, combined with the characteristics of MIPS and ARM architectures, and extracted a set of paths with the same start and end nodes using function call relationships, control flow graphs, and branching selection dependent strings.If the strings in the successfully verified set of paths have semantic conflict, it means that there is a hard-coded backdoor in the router firmware.In order to evaluate the detection effect of Stect, 1 074 collected device images were tested and compared with other backdoor detection methods.Experimental results show that Stect has a better detection effect compared with existing backdoor detection methods including Costin and Stringer: 8 hard-coded backdoor images detected from image data set, and the recall rate reached 88.89%

Advances in the Application of Aptamer Biosensors to the Detection of Aminoglycoside Antibiotics

Antibiotic abuse is becoming increasingly serious and the potential for harm to human health and the environment has aroused widespread social concern. Aminoglycoside antibiotics (AGs) are broad-spectrum antibiotics that have been widely used in clinical and animal medicine. Consequently, their residues are commonly found in animal-derived food items and the environment. A simple, rapid, and sensitive detection method for on-site screening and detection of AGs is urgently required. In recent years, with the development of molecular detection technology, nucleic acid aptamers have been successfully used as recognition molecules for the identification and detection of AGs in food and the environment. These aptamers have high affinities, selectivities, and specificities, are inexpensive, and can be produced with small batch-to-batch differences. This paper reviews the applications of aptamers for AG detection in colorimetric, fluorescent, chemiluminescent, surface plasmon resonance, and electrochemical sensors for the analysis in food and environmental samples. This study provides useful references for future research

Comparison of two models on simulating electric field in HVDC cable insulation

Space charge accumulation in cable insulation is one of the major technical problems in the further development of HVDC cables. A conductivity model and a bipolar charge transport model are developed to respectively calculate the space charge and electric field distribution in polymeric insulation. In this paper, both models are employed to simulate the field distribution in a medium voltage polymeric cable. Comparisons are made between theoretical and simulation results. The limitations of the conductivity model which is widely used in HVDC cable design are presented, and the results of the bipolar charge transport model are more consistent with the experimental observations. Moreover, transient current in the cable is simulated to anticipate the field distribution within the insulation when subjected to a thermal transient. The results suggest that the thermal transient can affect the space charge and electric field distribution significantly. A field inversion can only take place with higher temperature and larger temperature gradient, and this can be maintained even with temperature decreasing

A new model for Thomson-type actuator including the pressure buffer

The motion characteristics and flow field variation of Thomson-type actuator have been investigated in this article, in which a two-dimensional axisymmetric cylindrical coordinate model is constructed and described by a set of multi-physical equations reflecting the flow field, transient electromagnetic field, electric circuit, and mechanical motion. The motion performance of the actuator and the pressure drag caused by the high-speed movement of metal plate are analyzed under different opening speeds. It shows that the pressure drag has a strong buffer effect on the actuator. The influence of the laminar and standard k − ε models on the pressure distribution, velocity distribution, and motion characteristics is focused on. In comparison with the laminar model, the pressure drag of the turbulence model is much higher than the laminar model and is more beneficial for the buffer design of the mechanism

Modelling space charge in HVDC cable insulation

The design of high-voltage direct-current extruded cable is one of the most challenging issues in the cable industry, as the electric field distribution across the insulation can be strongly affected by the presence of space charge, which can subsequently affect its long-term reliability and life expectancy. In this study, the bipolar charge transport model was utilized to calculate space charge and field distribution in a polymeric cable insulation, and the result was compared with the one obtained by the conductivity model which is commonly used in the cable industry. It is shown that the simulation results of the bipolar charge transport model are more comparable with the previous experimental work, and the shortcomings of the conductivity model are presented. At last, the feasibility and potential issues of the new method are discussed for further development

A new species of Liobagrus Hilgendorf, 1878 (Teleostei, Siluriformes, Amblycipitidae) from the lower Changjiang River basin in southeast China

A new catfish species, Liobagrus chenhaojuni Chen, Guo & Wu, sp. nov., is described from the Tiaoxi River, a tributary of Taihu Lake, located in Zhejiang Province, China. This description is based on morphological characteristics and phylogenetic analysis. This species belongs to a group defined by the presence of a smooth posterior edge of the pectoral-fin spine and can be distinguished from other species in the group by a unique combination of characteristics, including: an upper jaw longer than the lower jaw; maxillary barbels reaching the middle of the pectoral fin; irregular blotches present on the lateral body; a rounded caudal-fin with a length ranging from 16.5% to 19.9% of the standard length; 39 to 41 post-Weberian vertebrae; and 15 to 17 anal-fin rays. The validity of this new species is further supported by the molecular phylogenetic analysis based on Cytb sequences

How should extra‐large Lugol‐unstained lesions of the esophagus be treated? Results from a population‐based cohort study

Abstract Background Current guidelines recommend only severe dysplasia and above (SDA) lesions of the esophageal squamous epithelium for clinical intervention. However, the histopathologic diagnosis derived from tissue biopsies may be subject to underestimation of severity. Methods 1073 participants from whom biopsies were taken at baseline chromoendoscopic examination in a population‐based screening trial were enrolled in this study. The size of the Lugol‐unstained lesions (LULs) was mainly analyzed. The outcome was defined as SDA lesions either identified at baseline screening, or during follow‐up, collectively referred to as the cumulative risk of SDA. Multivariable logistic regression models were used to evaluate the cumulative risk of SDA. Results One hundred and forty‐six SDA cases were identified in the study period. Participants with large LULs had a high cumulative incidence of SDA (cumulative incidence16–20mm: 55.88%; cumulative incidence>20mm: 76.92%) in the median of 7‐year duration. LULs of large size were significantly associated with a higher cumulative risk of SDA, regardless of the pathologic diagnosis (adjusted OR16–20mmvs.≤5mm = 21.02, 95% CI: 7.56–58.47; adjusted OR>20mmvs.≤5mm = 33.62, 95% CI: 11.79–95.87). Conclusions Results from this study suggest physician–patient shared decision‐making regarding clinical treatment or intensive surveillance should be carried out for LULs >20 mm in the esophagus, regardless of the histologic diagnosis. For those with LULs of 16–20 mm, intensive surveillance would also best be considered