No abstract

Vehicular Ad Hoc Networks (VANETs) have emerged mainly to improve road safety and traffic efficiency and provide user comfort. The performance of such networks' applications relies on the availability of accurate and recent mobility-information shared among vehicles. This means that misbehaving vehicles that share false mobility information can lead to catastrophic losses of life and property. However, the current solutions proposed to detect misbehaving vehicles are not able to cope with the dynamic vehicular context and the diverse cyber-threats, leading to a decrease in detection accuracy and an increase in false alarms. This paper addresses these issues by proposing a Hybrid and Multifaceted Context-aware Misbehavior Detection model (HCA-MDS), which consists of four phases: data-collection, context-representation, context-reference construction, and misbehavior detection. Data-centric and behavioral-detection-based features are derived to represent the vehicular context. An online and timely updated context-reference model is built using unsupervised nonparametric statistical methods, namely Kalman and Hampel filters, through analyzing the temporal and spatial correlation of the consistency between mobility information to adapt to the highly dynamic vehicular context. Vehicles' behaviors are evaluated locally and autonomously according to the consistency, plausibility, and reliability of their mobility information. The results from extensive simulations show that HCA-MDS outperforms existing solutions in increasing the detection rate by 38% and decreasing the false positive rate by 7%. These results demonstrate the effectiveness and robustness of the proposed HCA-MDS model to strengthen the security of VANET applications and protocols. INDEX TERMS Hybrid, context-aware, misbehavior detection, vehicular ad hoc network (VANET), false information attacks, Kalman Filter, Hampel Filter.

Electronic Health Records (EHR) are a rich repository of valuable clinical information that exist in primary and secondary care databases. In order to utilize EHRs for medical observational research a range of algorithms for automatically identifying individuals with a specific phenotype have been developed. This review summarizes and offers a critical evaluation of the literature relating to studies conducted into the development of EHR phenotyping systems. This review describes phenotyping systems and techniques based on structured and unstructured EHR data. Articles published on PubMed and Google scholar between 2013 and 2017 have been reviewed, using search terms derived from Medical Subject Headings (MeSH). The popularity of using Natural Language Processing (NLP) techniques in extracting features from narrative text has increased. This increased attention is due to the availability of open source NLP algorithms, combined with accuracy improvement. In this review, Concept extraction is the most popular NLP technique since it has been used by more than 50% of the reviewed papers to extract features from EHR. High-throughput phenotyping systems using unsupervised machine learning techniques have gained more popularity due to their ability to efficiently and automatically extract a phenotype with minimal human effort.

The cryptography employed against user files makes the effect of crypto-ransomware attacks irreversible even after detection and removal. Thus, detecting such attacks early, i.e. during pre-encryption phase before the encryption takes place is necessary. Existing crypto-ransomware early detection solutions use a fixed time-based thresholding approach to determine the pre-encryption phase boundaries. However, the fixed time thresholding approach implies that all samples start the encryption at the same time. Such assumption does not necessarily hold for all samples as the time for the main sabotage to start varies among different cryptoransomware families due to the obfuscation techniques employed by the malware to change its attack strategies and evade detection, which generates different attack behaviors. Additionally, the lack of sufficient data at the early phases of the attack adversely affects the ability of feature extraction techniques in early detection models to perceive the characteristics of the attacks, which, consequently, decreases the detection accuracy. Therefore, this paper proposes a Dynamic Pre-encryption Boundary Delineation and Feature Extraction (DPBD-FE) scheme that determines the boundary of the pre-encryption phase, from which the features are extracted and selected more accurately. Unlike the fixed thresholding employed by the extant works, DPBD-FE tracks the pre-encryption phase for each instance individually based on the first occurrence of any cryptography-related APIs. Then, an annotated Term Frequency-Inverse Document Frequency (aTF-IDF) technique was utilized to extract the features from runtime data generated during the pre-encryption phase of crypto-ransomware attacks. The aTF-IDF overcomes the challenge of insufficient attack patterns during the early phases of the attack lifecycle. The experimental evaluation shows that DPBD-FE was able to determine the pre-encryption boundaries and extract the features related to this phase more accurately compared to related works.

A large number of intelligent models for masked face recognition (MFR) has been recently presented and applied in various fields, such as masked face tracking for people safety or secure authentication. Exceptional hazards such as pandemics and frauds have noticeably accelerated the abundance of relevant algorithm creation and sharing, which has introduced new challenges. Therefore, recognizing and authenticating people wearing masks will be a long-established research area, and more efficient methods are needed for real-time MFR. Machine learning has made progress in MFR and has significantly facilitated the intelligent process of detecting and authenticating persons with occluded faces. This survey organizes and reviews the recent works developed for MFR based on deep learning techniques, providing insights and thorough discussion on the development pipeline of MFR systems. State-of-the-art techniques are introduced according to the characteristics of deep network architectures and deep feature extraction strategies. The common benchmarking datasets and evaluation metrics used in the field of MFR are also discussed. Many challenges and promising research directions are highlighted. This comprehensive study considers a wide variety of recent approaches and achievements, aiming to shape a global view of the field of MFR.