Exploração de Covert Channels de Rede sobre comunicações IEEE 802.15.4

The advancements in information and communication technology in the past decades have been converging into a new communication paradigm in which everything is expected to be interconnected with the heightened pervasiveness and ubiquity of the Internet of Things (IoT) paradigm. As these technologies mature, they are increasingly finding its way into more sensitive domains, such as Medical and Industrial IoT, in which safety and cyber-security are paramount. While the number of deployed IoT devices continues to increase annually, up to tens of billions of connected devices, IoT devices continue to present severe cyber-security vulnerabilities, which are worsened by challenges such as scalability, heterogeneity, and their often scarce computing capacity. Network covert channels are increasingly being used to support malware with stealthy behaviours, aiming at exfiltrating data or to orchestrate nodes of a botnet in a cloaked fashion. Nevertheless, the attention to this problem regarding underlying and pervasive IoT protocols such as the IEEE 802.15.4 has been scarce. Therefore, in this Thesis, we aim at analysing the performance and feasibility of such covertchannel implementations upon the IEEE 802.15.4 protocol to support the development of new mechanisms and add-ons that can effectively contribute to improve the current state of-art of IoT systems which rely on such, or similar underlying communication technologies.Os avanços nas tecnologias de informação e comunicação nas últimas décadas têm convergido num novo paradigma de comunicação, onde se espera que todos os intervenientes estejam interconectados pela ubiquidade do paradigma da Internet of Things (Internet das Coisas). Com a maturação destas tecnologias, elas têm-se vindo a infiltrar em domínios cada vez mais sensíveis, como nas aplicações médicas e industriais, onde a confiabilidade da informação e cyber-segurança são um fator crítico. Num contexto onde o número de dispositivos IoT continua a aumentar anualmente, já na ordem das dezenas de biliões de dispositivos interconectados, estes continuam, contudo, a apresentar severas vulnerabilidades no campo da cyber-segurança, sendo que os desafios como a escalabilidade, heterogeneidade e, na maioria das vezes, a sua baixa capacidade de processamento, tornam ainda mais complexa a sua resolução de forma permanente. Os covert channels de rede são cada vez mais um meio de suporte a malwares que apresentam comportamentos furtivos, almejando a extração de informação sensível ou a orquestração de nós de uma botnet de uma forma camuflada. Contudo, a atenção dada a este problema em protocolos de rede IoT abrangentes como o IEEE 802.15.4, tem sido escassa. Portanto, nesta tese, pretende-se elaborar uma análise da performance e da viabilidade da implementação de covert channels em modelos de rede onde figura o protocolo IEEE 802.15.4 de forma a suportar o desenvolvimento de novos mecanismos e complementos que podem efetivamente contribuir para melhorar a ciber-segurança de sistemas IoT que dependem do suporte destas tecnologias de comunicação

Archaeology of the Pleistocene-Holocene transition in Portugal: synthesis and prospects

The Tardiglacial of Portugal has been associated with the Magdalenian culture and lithic industries characterized by tool miniaturization, a diversity of microlith types, and the absence of a intentional blade production. The technological characterization, the chronology and the phasing of the Portuguese Magdalenian have been defined based on data recovered from open-air sites of the Estremadura region (Central Portugal). This paper presents an overview of the research undertaken over the last twenty-five years, including results from research and preventive archaeology fieldwork outside this region, namely in the Côa, Sabor and Vouga Valleys (northern Portugal), as well as in the Guadiana Valley and Algarve regions (southern Portugal). Our chronological boundaries are the Greenland Stadial 2-1b and the 8.2 ka event, from Early Magdalenian to Early Mesolithic. Regarding vegetation, deciduous Quercus underwent expansion during the warm phases of the Tardiglacial and retracted during cold ones, when pines increased. After the Solutrean, the faunal assemblages show a decrease in the variability of the represented species and an increase in fish, birds, small mammals and rabbits (Oryctolagus cuniculus). Concerning the cultural sequence, the Middle Magdalenian remains uncharacterised. After the Upper Magdalenian, and thenceforward, the use of local raw materials and of cores-on-flakes (burin or carinated endscraper type) for bladelet production gradually increased. In terms of lithic armatures typology, a four-stage sequence can be discerned: 1) Upper Magdalenian with axial points rather than backed bladelets, quite common in previous phases; 2) Final Magdalenian with an increase in the diversity of armature types; 3) Azilian with geometric microliths, curved backed points (Azilian points) and Malaurie points, and 4) Early Mesolithic without retouched bladelet tools or at best a persistence of Azilian armature types. There were some changes in the Palaeolithic rock art of the Douro basin between phase 3 (Final Magdalenian) and phase 4 (Late Azilian): figurative animal representations give place to animal depictions characterized by their geometrical bodies, often filled-in, and red deer becomes the best-represented animal.FCT: PTDC/EPH-ARQ/0326/2014info:eu-repo/semantics/publishedVersio

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)