1,720,980 research outputs found
Checking the Expressivity of Firewall Languages
No full textDesigning and maintaining firewall configurations is hard, also for expert system administrators. Indeed, policies are made of a large number of rules and are written in low-level configuration languages that are specific to the firewall system in use. As part of a larger group, we have addressed these issues and have proposed a semantic-based transcompilation pipeline. It is supported by FWS, a tool that analyses a real configuration and ports it from a firewall system to another. To our surprise, we discovered that some configurations expressed in a real firewall system cannot be ported to another system, preserving the semantics. Here we outline the main reasons for the detected differences between the firewall languages, and describe F2F, a tool that checks if a given configuration in a system can be ported to another system, and reports its user on which parts cause problems and why
FWS: Analyzing, maintaining and transcompiling firewalls
No full textFirewalls are essential for managing and protecting computer networks. They permit specifying which packets are allowed to enter a network, and also how these packets are modified by IP address translation and port redirection. Configuring a firewall is notoriously hard, and one of the reasons is that it requires using low level, hard to interpret, configuration languages. Equally difficult are policy maintenance and refactoring, as well as porting a configuration from one firewall system to another. To address these issues we introduce a pipeline that assists system administrators in checking if: (i) the intended security policy is actually implemented by a configuration; (ii) two configurations are equivalent; (iii) updates have the desired effect on the firewall behavior; (iv) there are useless or redundant rules; additionally, an administrator can (v) transcompile a configuration into an equivalent one in a different language; and (vi) maintain a configuration using a generic, declarative language that can be compiled into different target languages. The pipeline is based on IFCL, an intermediate firewall language equipped with a formal semantics, and it is implemented in an open source tool called FWS. In particular, the first stage decompiles real firewall configurations for iptables, ipfw, pf and (a subset of) Cisco IOS into IFCL. The second one transforms an IFCL configuration into a logical predicate and uses the Z3 solver to synthesize an abstract specification that succinctly represents the firewall behavior. System administrators can use FWS to analyze the firewall by posing SQL-like queries, and update the configuration to meet the desired security requirements. Finally, the last stage allows for maintaining a configuration by acting directly on its abstract specification and then compiling it to the chosen target language. Tests on real firewall configurations show that FWS can be fruitfully used in real-world scenarios
FWS: Analyzing, maintaining and transcompiling firewalls
No full textFirewalls are essential for managing and protecting computer networks. They permit specifying which packets are allowed to enter a network, and also how these packets are modified by IP address translation and port redirection. Configuring a firewall is notoriously hard, and one of the reasons is that it requires using low level, hard to interpret, configuration languages. Equally difficult are policy maintenance and refactoring, as well as porting a configuration from one firewall system to another. To address these issues we introduce a pipeline that assists system administrators in checking if: (i) the intended security policy is actually implemented by a configuration; (ii) two configurations are equivalent; (iii) updates have the desired effect on the firewall behavior; (iv) there are useless or redundant rules; additionally, an administrator can (v) transcompile a configuration into an equivalent one in a different language; and (vi) maintain a configuration using a generic, declarative language that can be compiled into different target languages. The pipeline is based on IFCL, an intermediate firewall language equipped with a formal semantics, and it is implemented in an open source tool called FWS. In particular, the first stage decompiles real firewall configurations for iptables, ipfw, pf and (a subset of) Cisco IOS into IFCL. The second one transforms an IFCL configuration into a logical predicate and uses the Z3 solver to synthesize an abstract specification that succinctly represents the firewall behavior. System administrators can use FWS to analyze the firewall by posing SQL-like queries, and update the configuration to meet the desired security requirements. Finally, the last stage allows for maintaining a configuration by acting directly on its abstract specification and then compiling it to the chosen target language. Tests on real firewall configurations show that FWS can be fruitfully used in real-world scenarios
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effect Semantics for Quantum Process Calculi
Get PDFThe development of quantum communication protocols sparked the interest in quantum extensions of process calculi and behavioural equivalences, but defining a bisimilarity that matches the observational properties of a quantum-capable system is a surprisingly difficult task. The two proposals explicitly addressing this issue, qCCS and lqCCS, do not define an algorithmic verification scheme: the
bisimilarity of two processes is proven by comparing their behaviour under all input states. We introduce a new semantic model based on effects, i.e. probabilistic predicates on quantum states that represent their observable properties. We define and investigate the properties of effect distributions
and effect labelled transition systems (eLTSs), generalizing probability distributions and probabilistic labelled transition systems (pLTSs), respectively. As a proof of concept, we provide an eLTS-based semantics for a minimal quantum process algebra, which we prove sound and complete with respect to the observable probabilistic behaviour of quantum processes. To the best of our knowledge, ours is the first algorithmically verifiable proposal that abides to the properties of quantum theory
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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