Delay-CJ:A novel cryptojacking covert attack method based on delayed strategy and its detection

Cryptojacking is a type of resource embezzlement attack,wherein an attacker secretly executes the cryptocurrency mining program in the target host to gain profits.It has been common since 2017,and in fact,it once became the greatest threat to network security.To better prove the attack ability the harm caused by cryptojacking,this paper proposes a new covert browser-based mining attack model named Delay-CJ,this model was deployed in a simulation environment for evaluation.Based on the general framework of cryptojacking,Delay-CJ adds hybrid evasion detection techniques and applies the delayed execution strategy specifically for video websites in the prototype implementation.The results show that the existing detection methods used for testing may become invalid as result of this model.In view of this situation,to achieve a more general and robust detection scheme,we built a cryptojacking detection system named CJDetector,which is based on cryptojacking process features.Specifically,it identifies malicious mining by monitoring CPU usage and analyzing the function call information.This system not only effectively detects the attack in our example but also has universal applicability.The recognition accuracy of CJDetector reaches 99.33%.Finally,we tested the web pages in Alexa 50K websites to investigate cryptojacking activity in the real network.We found that although cryptojacking is indeed on the decline,it remains a part of network security threats that cannot be ignored.

十三氟辛醇接枝改性三聚氰胺树脂的合成及其疏水性能

以1H,1H,2H,2H-十三氟-1-辛醇(PF-OH)为改性剂,三聚氰胺和多聚甲醛为原料,二甲基乙酰胺为反应介质,合成了一系列PF-OH接枝改性三聚氰胺树脂(MF-F)。FT-IR和固体;C NMR结果表明PF-OH与三聚氰胺树脂(MF树脂)成功接枝。采用XPS、接触角测定仪和TG对材料进行测定,结果表明:PF-OH的接枝提升MF-F材料的疏水性能,氟元素向材料的表面迁移并发生富集;当PF-OH的摩尔分数为3.0%(以三聚氰胺物质的量计),其水接触角由67.83°增至103.50°,表面自由能由44.5 mN/m降至21.1 mN/m。PF-OH的引入提高MF-F材料的热稳定性,其T;(失重5%温度)、T;(失重80%温度)和790℃时的残留率均提高。

Tibetan Plateau Relict Snakes of the Genus Thermophis and Their Relationship to New World Relict Snakes

The complete mitochondrial NADH dehydrogenase subunit 2(ND2) gene sequences of two species of Thermophis, T. baileyi and T. zhaoermii, were sequenced and compared to those of 86 sequences from other snakes(74 from Caenophidia and 12 from Henophidia). By using Bayesian inference(BI) and maximum likehood(ML) approaches, Thermophis was demonstrated as the sister group to the North American relicts of Dipsadinae, and rooted in Central and South American members of this subfamily. The results suggest that the closest relatives of Thermophis are the North American relicts, and thus support the hypothesis for an Asian-North American origin of xenodontine snakes as suggested by Vidal et al.(2000). Extensive sampling of Asian snakes and American dipsadines is needed to further test this hypothesis in the future.

Meeting 24-h Movement Guidelines is Related to Better Academic Achievement:Findings from the YRBS 2019 Cycle

This research is designed to investigate the relationship between the 24-h movement guidelines(24-HMG)and self-reported academic achievement(AA)using nationally representative data derived from the 2019 U.S.National Youth Risk Behaviour Survey.A multiple-stage cluster sampling procedure has been adopted to ensure a representative sample(N=9127 adolescents;mean age=15.7 years old;male%=49.8%).Logistic regression has been adopted to obtain the odds ratio(OR)regarding the associations between adherence to 24-HMG and AA while controlling for ethnicity,body mass index,sex and age.The prevalence of meeting the 24-h movement guidelines in isolation and combination varied greatly(physical activity=23.3%,screen time=32.5%,sleep=22.3%,and 24-HMG=2.8%),while the percentage of highest-class AA was 42.5%.Compared with the situation when none of 24-HMG is met,the achievement of any of the combined guidelines(except for meeting the physical activity guidelines)was significantly associated with higher odds of achieving first-class AA.Meeting the sleep guideline had 1.42 times increased likelihood to achieve highest-class AA as compared with not meeting the sleep guideline.Meeting screen time guidelines and physical activity guidelines,respectively,were 1.32 and 1.13 times more likely to report first-class AA;but meeting the guidelines of physical activity was not significantly related to AA.Meeting the 24-HMG had the highest odds of achieving first-class AA(OR=2.01,95%CI:1.47-2.73).In both sexes,adolescents who met 24-HMG self-reported better AA(boys OR=2.05,95%CI:1.34-3.15;girls OR=2.26,95%CI:1.36-3.76).Significant relationships were observed in adolescents from 9-10th grade,but not higher grades.Our research findings suggest that optimal movement behaviours can be seen as an important element to better academic achievement among U.S.adolescents.Future studies can adopt our discoveries to promote adolescents’academic achievement through implementing optimal 24-h movement behaviour patterns.

Pre-post notation is questionable in effectively specifying operations of object-oriented systems

There is a growing tendency for people in the community of object-oriented methods to use preand post-conditions to write formal specifications for opera- tions （methods） of classes. The motivation for trying to take advantage of well established formalism in precisely defining the functionality of operations is laudable, but unfortunately this exercise may be flawed because the use of pre- and post-conditions containing method calls （or similar） with side effects are likely to cause confusion in the interpretation of specifications. This paper analyzes, with comprehensible examples, why using pre-post notation is not effective to specify operations in objectoriented systems in general, discusses existing approaches to using pre-post notation for object-oriented systems, and offers some solutions to the problem.

Formal engineering methods for software quality assurance

Conventional software engineering on the basis of informal or semi-formal methods is facing tremendous challenges in ensur- ing software quality. Formal methods have attempted to address these challenges by introducing mathematical notation and calculus to support formal specification, refinement, and verification in software development. Their theoretical contributions to the discipline of software engineering are significant. However, in spite of their potential in improving the controllability of software process and reliability, formal methods are generally difficult to apply to large-scale and complex systems in practice because of many constraints （e.g., limited expertise, complexity, changing requirements, and theoretical limitations）. Re- searches on the integration of formal methods into conventional software engineering technologies and processes are likely to create effective ways to transfer formal methods to industry for software productivity and quality. One of the examples is the development of the structured object-oriented formal language （SOFL） and its associated SOFL method for industrial software development.