Towards operational measures of computer security

Ideally, a measure of the security of a system should capture quantitatively the intuitive notion of ‘the ability of the system to resist attack’. That is, it should be operational, reflecting the degree to which the system can be expected to remain free of security breaches under particular conditions of operation (including attack). Instead, current security levels at best merely reflect the extensiveness of safeguards introduced during the design and development of a system. Whilst we might expect a system developed to a higher level than another to exhibit ‘more secure behaviour’ in operation, this cannot be guaranteed; more particularly, we cannot infer what the actual security behaviour will be from knowledge of such a level. In the paper we discuss similarities between reliability and security with the intention of working towards measures of ‘operational security’ similar to those that we have for reliability of systems. Very informally, these measures could involve expressions such as the rate of occurrence of security breaches (cf rate of occurrence of failures in reliability), or the probability that a specified ‘mission’ can be accomplished without a security breach (cf reliability function). This new approach is based on the analogy between system failure and security breach. A number of other analogies to support this view are introduced. We examine this duality critically, and have identified a number of important open questions that need to be answered before this quantitative approach can be taken further. The work described here is therefore somewhat tentative, and one of our major intentions is to invite discussion about the plausibility and feasibility of this new approach

Evaluating On-line Model Checking in UPPAAL-SMC using a Laser Tracheotomy Case Study

On-line model checking is a variant of model checking that evaluates properties of a system concurrently while deployed, which allows overcoming limitations of inaccurate system models. In this paper we conduct a laser tracheotomy case study to evaluate the feasibility of using the statistical model checker UPPAAL-SMC for on-line model checking in a medical application. Development of automatic on-line model checking relies on the precision of the prediction and real-time capabilities as real-time requirements must be met. We evaluate the case study with regards to these qualities and our results show that using UPPAAL-SMC in an on-line model checking context is practical: relative prediction errors were only 2% on average and guarantees could be established within reasonable time during our experiments

08302 Abstracts Collection -- Countering Insider Threats

From July 20 to July 25, 2008, the Dagstuhl Seminar 08302 ``Countering Insider Threats \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

10341 Abstracts Collection -- Insider Threats: Strategies for Prevention, Mitigation, and Response

From August 22 to 26, 2010, the Dagstuhl Seminar 10341 ``Insider Threats: Strategies for Prevention, Mitigation, and Response\u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

History-sensitive versus future-sensitive approaches to security in distributed systems

We consider the use of aspect-oriented techniques as a flexible way to deal with security policies in distributed systems. Recent work suggests to use aspects for analysing the future behaviour of programs and to make access control decisions based on this; this gives the flavour of dealing with information flow rather than mere access control. We show in this paper that it is beneficial to augment this approach with history-based components as is the traditional approach in reference monitor-based approaches to mandatory access control. Our developments are performed in an aspect-oriented coordination language aiming to describe the Bell-LaPadula policy as elegantly as possible. Furthermore, the resulting language has the capability of combining both history- and future-sensitive policies, providing even more flexibility and power.Comment: In Proceedings ICE 2010, arXiv:1010.530

Magnetic orientation of the Common Toad: establishing an arena approach for adult anurans

<p>Abstract</p> <p>Background</p> <p>Magnetic orientation is a taxonomically widespread phenomenon in the animal kingdom, but has been little studied in anuran amphibians. We collected Common Toads (<it>Bufo bufo</it>) during their migration towards their spawning pond and tested them shortly after displacement for possible magnetic orientation in arena experiments. Animals were tested in two different set-ups, in the geomagnetic field and in a reversed magnetic field. To the best of our knowledge, this is the first study testing orientation of adult anurans with a controlled magnetic field of a known strength and alignment.</p> <p>Results</p> <p>After displacement, toads oriented themselves unimodally under the geomagnetic field, following their former migration direction (d-axis). When the magnetic field was reversed, the distribution of bearings changed from a unimodal to a bimodal pattern, but still along the d-axis. The clustering of bearings was only significant after the toads reached the outer circle, 60.5 cm from their starting point. At a virtual inner circle (diameter 39 cm) and at the start of the experiment, orientation of toads did not show any significant pattern.</p> <p>Conclusions</p> <p>The experimental set-up used in our study is suitable to test orientation behaviour of the Common Toad. We speculate that toads had not enough time to relocate their position on an internal map. Hence, they followed their former migration direction. Bimodality in orientation when exposed to the reversed magnetic field could be the result of a cue conflict, between magnetic and possibly celestial cues. For maintaining their migration direction toads use, at least partly, the geomagnetic field as a reference system.</p

Sphingosine 1-phosphate modulates antigen capture by murine langerhans cells via the S1P2 receptor subtype

Dendritic cells (DCs) play a pivotal role in the development of cutaneous contact hypersensitivity (CHS) and atopic dermatitis as they capture and process antigen and present it to T lymphocytes in the lymphoid organs. Recently, it has been indicated that a topical application of the sphingolipid sphingosine 1-phosphate (S1P) prevents the inflammatory response in CHS, but the molecular mechanism is not fully elucidated. Here we indicate that treatment of mice with S1P is connected with an impaired antigen uptake by Langerhans cells (LCs), the initial step of CHS. Most of the known actions of S1P are mediated by a family of five specific G protein-coupled receptors. Our results indicate that S1P inhibits macropinocytosis of the murine LC line XS52 via S1P2 receptor stimulation followed by a reduced phosphatidylinositol 3-kinase (PI3K) activity. As down-regulation of S1P2 not only diminished S1P-mediated action but also enhanced the basal activity of LCs on antigen capture, an autocrine action of S1P has been assumed. Actually, S1P is continuously produced by LCs and secreted via the ATP binding cassette transporter ABCC1 to the extracellular environment. Consequently, inhibition of ABCC1, which decreased extracellular S1P levels, markedly increased the antigen uptake by LCs. Moreover, stimulation of sphingosine kinase activity, the crucial enzyme for S1P formation, is connected not only with enhanced S1P levels but also with diminished antigen capture. These results indicate that S1P is essential in LC homeostasis and influences skin immunity. This is of importance as previous reports suggested an alteration of S1P levels in atopic skin lesions

Das Leben protestantischer Pastoren in Deutschland vom Ende des 17. Jahrhunderts bis zur Mitte des 19. Jahrhunderts

Nicht angegebe

Estudo de viabilidade econômica e da implantação de condomínio horizontal de lotes para fins residenciais no município de Venâncio Aires

O condomínio horizontal de lotes consiste em um formato de habitação diferente das demais existentes nas cidades com crescimento urbano acelerado, e suas principais características estão relacionadas ao conforto e a segurança. Este trabalho tem como objetivo apresentar o estudo de viabilidade econômica através de levantamento de despesas necessárias para a implantação e da simulação de cenários para a venda dos lotes, na cidade de Venâncio Aires, e ainda demonstrar os procedimentos para que este modelo de projeto possa ser implantado. Inicialmente realizou-se o projeto urbanístico e o pré-dimensionamento da rede de água, esgoto, elétrica e pluvial. Em seguida, foi realizado o cálculo estimado de despesas que ocorrerão durante a construção do empreendimento, o que resultou em um valor total de R$9.252.752,32, referentes à construção das edificações e áreas de uso recreativo, da infraestrutura e demais custos de operação. Após essa etapa foi desenvolvido um cronograma físico-financeiro para identificar o valor total de despesas geradas a cada mês, durante o período de construção e, por fim, foi realizado o estudo de viabilidade econômica para este empreendimento, utilizando simulações para a venda dos lotes. A partir das simulações que consideraram diferentes cenários para a venda dos lotes, foi possível concluir que a instalação deste tipo de empreendimento em Venâncio Aires é viável. Concluiu-se, também, que o valor mínimo praticável, para a venda dos imóveis deverá ser de R$ 135.000,00, que possibilita uma lucratividade superior a 6,45 %