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Data Privacy in Ride-Sharing Services: From an Analysis of Common Practices to Improvement of User Awareness
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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
Georeplizierte byzantinisch fehlertolerante Zustandsmaschinenreplikation mit niedriger Latenz
Get PDFProtocols tolerating Byzantine faults allow a service to maintain correctness even if some of its parts misbehave.
However, they significantly increase the overhead for processing client requests.
Especially for geo-replicated systems, response times can grow to several hundred milliseconds.
As the communication latency between remote locations is limited by the speed of light, minimizing these delays requires optimized protocols.
This thesis investigates different approaches to reduce the response times of strongly consistent Byzantine fault-tolerant state-machine replication protocols that only require a low number of replicas in a geo-replicated setting.
It first reviews the steps necessary to process client requests with strong consistency and derives approaches to minimize the delay introduced by the client communication, the agreement and the execution.
To minimize the latency for submitting a client request to the system, each replica is enabled to immediately initiate the ordering for a request, thus allowing a client to communicate with the nearest replica.
The proposed Byzantine fault-tolerant egalitarian protocol, which only uses the minimum number of replicas to tolerate faults, accordingly removes the need for a central leader replica by instead agreeing on conflicts between requests.
The agreement can complete on a fast path if the involved replicas propose matching conflicts.
Before execution, requests are sorted according to their conflicts to ensure a consistent order across replicas.
To minimize the latency of the agreement protocol, this thesis introduces an approach based on the architecture of modern clouds.
The replicas are split into a central agreement group, which determines the execution order for all client requests, with at least replicas and multiple execution groups with only replicas.
Each group of replicas is located in one region, with its replicas distributed across multiple availability zones to minimize the risk of correlated failures.
Thus, replicas in a group can communicate with each other with low latency, thereby allowing the agreement to work with low latency.
The groups use an abstraction called inter-regional message channel, which allows them to exchange client requests and the agreement results reliably.
To minimize the execution latency, this thesis reduces response-time spikes caused by the periodic creation of checkpoints during which the request execution must be paused.
Instead, it introduces a concurrent state-capture phase, which starts before reaching the point at which to create the checkpoint.
The resulting fuzzy snapshot together with a list of state modifications made by requests executed in the meantime, can be combined into a regular checkpoint that is identical on all replicas.
The application interface offers two variants providing different trade-offs regarding simplicity and efficiency.
These approaches successfully reduce the client-perceived response times while also reducing the performance variation caused by different configurations and periodic tasks.Protokolle, die byzantinische Fehler tolerieren, ermöglichen es einem Dienst sich korrekt zu verhalten, selbst wenn Teile von ihm Fehlverhalten zeigen.
Allerdings erhöht dies den Aufwand zur Verarbeitung von Nutzeranfragen deutlich.
Insbesondere bei georeplizierten Systemen, können die Antwortzeiten auf mehrere hundert Millisekunden steigen.
Da die Kommunikationslatenz zwischen entfernten Orten durch die Lichtgeschwindigkeit beschränkt wird, sind optimierte Protokolle nötig, um diese Verzögerungen zu minimieren.
Diese Dissertation untersucht Ansätze, um die Antwortzeiten von stark konsistenten, byzantinisch fehlertoleranten Zustandsmaschinenreplikationsprotokollen im Kontext von Georeplikation zu reduzieren, die nur eine geringe Anzahl an Replikaten benötigen.
Dazu werden zuerst die für die stark konsistente Verarbeitung von Nutzeranfragen nötigen Schritte betrachtet und daraus Ansätze abgeleitet, die Verzögerungen durch die Kommunikation mit dem Nutzer, die Einigung und die Ausführung minimieren.
Zum Minimieren der Latenz für den Versand einer Nutzeranfrage an das System wird jedem Replikat ermöglicht, die Einigung einer Anfrage sofort zu starten, sodass der Nutzer mit dem nächstgelegenen Replikat kommunizieren kann.
Das vorgeschlagene byzantinisch fehlertolerante egalitäre Protokoll, das nur das Minimum von Replikaten zum Tolerieren vom Fehlern benötigt, ermöglicht es dementsprechend ohne ein zentrales Anführerreplikat auszukommen, indem sich auf Abhängigkeiten zwischen Anfragen geeinigt wird.
Falls die beteiligten Replikate die gleichen Abhängigkeiten vorschlagen, kann die Einigung im Schnelldurchlauf abgeschlossen werden.
Vor der Ausführung werden Anfragen dann entsprechend ihrer Abhängigkeiten sortiert, um eine konsistente Ausführungsreihenfolge über alle Replikate zu garantieren.
Zum Minimieren der Latenz des Einigungsprotokolls stellt diese Dissertation einen Ansatz vor, der die Architektur moderner Cloud-Plattformen ausnutzt.
Die Replikate werden in eine zentrale Einigungsgruppe, die die Ausführungsreihenfolge der Nutzeranfragen festlegt und aus Replikaten besteht, und mehrere Ausführungsgruppen mit jeweils nur Replikaten aufgeteilt.
Jede Gruppe läuft innerhalb einer Region, wobei die einzelnen Replikate auf verschiedene Verfügbarkeitszonen verteilt sind, um das Risiko gleichzeitiger Ausfälle zu minimieren.
Dadurch können Replikate einer Gruppe miteinander mit niedriger Latenz kommunizieren, was wiederum die Einigung mit niedriger Latenz ermöglicht.
Die Gruppen nutzen eine als interregionaler Nachrichtenkanal bezeichnete Abstraktion, die den zuverlässigen Austausch von Nutzeranfragen und Einigungsergebnissen ermöglicht.
Zum Minimieren der Ausführungslatenz reduziert diese Dissertation Antwortzeitspitzen, die durch das periodische Erstellen von Sicherungspunkten hervorgerufen werden, währenddessen die Anfrageausführung pausiert werden muss.
Stattdessen wird eine nebenläufige Zustandssicherungsphase eingeführt, die bereits startet, bevor der nächste Sicherungspunkt erstellt werden muss.
Der hierbei entstehende unscharfe Sicherungspunkt kann zusammen mit einer Liste von in der Zwischenzeit erfolgten Zustandsmodifikationen wieder in einen normalen Sicherungspunkt umgewandelt werden, der auf allen Replikaten übereinstimmt.
Die Anwendungsschnittstelle bietet dabei zwei Varianten an, die sich hinsichtlich Einfachheit und Effizienz unterscheiden.
Diese Ansätze ermöglichen es die Antwortzeiten aus Sicht des Nutzers zu optimieren, sowie auch Leistungsschwankungen durch unterschiedliche Systemkonfigurationen oder periodische Aufgaben zu reduzieren
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
Adding dynamic reconfiguration support to JBoss AOP
Get PDFThe majority of aspect-oriented middlewares supporting dynamic aspect weaving fail to preserve important safety properties while weaving or unweaving a distributed aspect at runtime. This position paper looks in particular at the safety properties of structural integrity and global state consistency. Preserving these two safety properties in the presence of dynamic change has already been extensively addressed in the space of dynamic reconfiguration of component-based distributed systems. As will be argued in this position paper, existing coordination protocols developed in this space can be largely reused for distributed aspect weaving provided that some small adaptations are made to account for the aspect-oriented composition mechanisms. To demonstrate results and as a proof-of-concept, we describe how we have ported the NeCoMan dynamic reconfiguration support on top of the JBoss AOP framework. As a result, system-wide consistency can be preserved in JBoss when weaving or unweaving a distributed aspect at runtime. Copyright 2007 ACM.status: Publishe
A Wide Network Scanning for Discovery of UDP-Based Reflectors in the Nordic Countries
No full textDistributed Reflective Denial of Service (DRDoS) attacks exploit Internet facing devices with the purpose to involve them in DoS incidents. In turn, these devices unwittingly amplify and redirect the attack traffic towards the victim. As a result, this traffic causes the extortion of the target’s network bandwidth and computation resources. The current work evaluates the amplification and reflective potentials of four UDP-based protocols, which are constantly reported as facilitators to DoS attacks. These are Simple Service Discovery Protocol (SSDP), Simple Network Management Protocol (SNMP), Constrained Application Protocol (CoAP) and Web Services Dynamic Discovery (WSD). Specifically, we conduct a countrywide network scanning across the four main Nordic countries, i.e., Denmark, Finland, Norway and Sweden, and enumerate the devices that respond to any of our probes and hence they can be exploited in DoS attacks. For each of the discovered devices, we assess its amplification capabilities in terms of Bandwidth Amplification Factor (BAF) and Packet Amplification Factor (PAF) that can contribute to a DoS incident. The outcomes show that from the four examined protocols, SSDP and SNMP are the most beneficial protocols from an attacker’s perspective, as a multitudinous group of reflectors is identified in each of the considered countries. Even worst, a significant portion of these devices produced a BAF over 30, a BAF that can multiply significantly the attack traffic stemming from the attacker’s side and hence causes a devastating impact on the victim’s infrastructure.</p
Actionable Cyber Threat Intelligence for Automated Incident Response
No full textApplying Cyber Threat Intelligence for active cyber defence, while potentially very beneficial, is currently limited to predominantly manual use. In this paper, we propose an automated approach for using Cyber Threat Intelligence during incident response by gathering Tactics, Techniques and Procedures available on intelligence reports, mapping them to network incidents, and then using this map to create attack patterns for specific threats. We consider our method actionable because it provides the operator with contextualised Cyber Threat Intelligence related to observed network incidents in the form of a ranked list of potential related threats, all based on patterns matched with the incidents. We evaluate our approach with publicly available samples of different malware families. Our analysis of the results shows that our method can reliably match network incidents with intelligence reports and relate them to these threats. The approach allows increasing the automation of its use, thus addressing one of the major limiting factors of effective use of suitable Cyber Threat Intelligence.</p
Honeysweeper:Towards stealthy Honeytoken fingerprinting techniques
Get PDFThe increased number of data breaches and sophisticated attacks have created a need for early detection mechanisms. Reports indicate that it may take up to 200 days to identify a data breach and entail average costs of up to $4.85 million. To cope with cyber-deception approaches like honeypots have been used for proactive attack detection and as a source of data for threat analysis. Honeytokens are a subset of honeypots that aim at creating deceptive layers for digital entities in the form of files and folders. Honeytokens are an important tool in the proactive identification of data breaches and intrusion detection as they raise an alert the moment a deceptive entity is accessed. In such deception-based defensive tools, it is key that the adversary does not detect the presence of deception. However, recent research shows that honeypots and honeytokens may be fingerprinted by adversaries. Honeytoken fingerprinting is the process of detecting the presence of honeytokens in a system without triggering an alert. In this work, we explore potential fingerprinting attacks against the most common open-source honeytokens. Our findings suggest that an advanced attacker can identify the majority of honeytokens without triggering an alert. Furthermore, we propose methods that help in improving the deception layer, the information received from the alerts, and the design of honeytokens
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