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  • 101.
    Momen, Nurul
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Pulls, Tobias
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Fritsch, Lothar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    How much Privilege does an App Need? Investigating Resource Usage of Android Apps2017In: Proceedings of the Fifteenth International Conference on Privacy, Security and Trust – PST 2017 (IEEE proceedings pendings), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Arguably, one of the default solutions to many of today’s everyday errands is to install an app. In order to deliver a variety of convenient and user-centric services, apps need to access different types of information stored in mobile devices, much of which is personal information. In principle, access to such privacy sensitive data should be kept to a minimum. In this study, we focus on privilege utilization patterns by apps installed on Android devices. Though explicit consent is required prior to first time access to the resource, the unavailability of usage information makes it unclear when trying to reassess the users initial decision. On the other hand, if granted privilege with little or no usage, it would suggest the likely violation of the principle of least privilege. Our findings illustrate a plausible requirement for visualising resource usage to aid the user in their decision- making and finer access control mechanisms. 

  • 102.
    Rajiullah, Mohammad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Priority Based Delivery of PR-SCTP Messages in a Syslog Context2011In: Access networks, Springer, 2011, p. 299-310Conference paper (Refereed)
    Abstract [en]

    Unquestionably, syslog provides the most popular and easily manageable computer system logging environment. In a computer network, syslog messages are used for several purposes such as for optimizing system performance, logging user's actions and investigating malicious activities. Due to all these essential utilities, a competent transport service for syslog messages becomes important. Most of the current syslog implementations use either the unreliable UDP protocol or the more costly reliable TCP protocol. Neither of these protocols can provide both timeliness and reliability, while transporting inherently prioritized syslog messages in a congested network. In this paper, we both propose and evaluate the use of PR-SCTP, an existing partial reliability extension of the SCTP transport protocol, as a candidate transport service for the next generation syslog standard. In our emulation based experimental results, PR-SCTP shows better performance than TOP in terms of average delay for message transfer. Furthermore, PR-SCTP exhibits less average packet loss than UDP. In both cases, PR-SCTP exploits priority properties of syslog messages during loss recovery.

  • 103.
    Rajiullah, Mohammad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lundin, Reine
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Performance Analysis and Improvement of PR-SCTP for Small Messages2013In: Computer Networks, ISSN 1389-1286, Vol. 57, no 18, p. 3967-3986Article in journal (Refereed)
    Abstract [en]

    PR-SCTP, a partially reliable extension of SCTP, provides a flexible QoS trade-off between timeliness and reliability for application traffic. However, the performance of PR-SCTP can be reduced due to certain traffic characteristics and network scenarios. Previously, we proposed a NR-SACK based optimization for PR-SCTP. In this work we extensively evaluate and analyze the performance of PR-SCTP with NR-SACKs using different network scenarios. Moreover, we compare the performance of our NR-SACK based PR-SCTP with existing transport protocols for syslog traffic. In the evaluation, we use real syslog traces from an operational syslog system. The results indicate that NR-SACKs based PR-SCTP significantly improves the overall message transfer delay as compared to SCTP and TCP.

  • 104.
    Rajiullah, Mohammad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lundin, Reine
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Data Modeling and Transport of Syslog Messages2011Conference paper (Refereed)
  • 105.
    Rajiullah, Mohammad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lundin, Reine
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Syslog Performance: Data Modeling and Transport2011In: Proceedings of the 3rd International Workshop on Security and Communication Networks (IWSCN 2011), Norway: IEEE Press, 2011, p. 31-37Conference paper (Refereed)
    Abstract [en]

    Syslog is one of the basic methods for event logging in computer networks. Log messages that are generated by syslog can be used for a number of purposes, including optimizing system performance, system auditing, and investigating malicious activities in a computer network. Considering all these attractive uses, both timeliness and reliability is needed when syslog messages are transported over a network. The unreliable transport protocol UDP was specified in the original syslog specification; later a reliable transport service based on TCP was also proposed. However, TCP is a costly alternative in terms of delay. In our previous work, we introduced the partially reliable extension of SCTP, PR-SCTP, as a transport service for syslog, trading reliability against timeliness by prioritizing syslog messages. In this work, we first model syslog data using real syslog traces from an operational network. The model is then used as input in the performance evaluation of PR-SCTP. In the experiments, real congestion is introduced in the network by running several competing flows. Although PR-SCTP clearly outperformed TCP and SCTP in our previous work, our present evaluations show that PR-SCTP performance is largely influenced by the syslog data size characteristics

  • 106.
    Voronkov, Artem
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Iwaya, Leonardo H
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Martucci, Leonardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Systematic Literature Review on Usability of Firewall Configuration2018In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 50, no 6, article id 87Article in journal (Refereed)
    Abstract [en]

    Firewalls are network security components that handle incoming and outgoing network traffic based on a set of rules. The process of correctly configuring a firewall is complicated and prone to error, and it worsens as the network complexity grows. A poorly configured firewall may result in major security threats; in the case of a network firewall, an organization’s security could be endangered, and in the case of a personal firewall, an individual computer’s security is threatened. A major reason for poorly configured firewalls, as pointed out in the literature, is usability issues. Our aim is to identify existing solutions that help professional and non-professional users to create and manage firewall configuration files, and to analyze the proposals in respect of usability. A systematic literature review with a focus on the usability of firewall configuration is presented in the article. Its main goal is to explore what has already been done in this field. In the primary selection procedure, 1,202 articles were retrieved and then screened. The secondary selection led us to 35 articles carefully chosen for further investigation, of which 14 articles were selected and summarized. As main contributions, we propose a taxonomy of existing solutions as well as a synthesis and in-depth discussion about the state of the art in firewall usability. Among the main findings, we perceived that there is a lack (or even an absence) of usability evaluation or user studies to validate the proposed models. Although all articles are related to the topic of usability, none of them clearly defines it, and only a few actually employ usability design principles and/or guidelines.

  • 107.
    Voronkov, Artem
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Martucci, Leonardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Challenges in Managing Firewalls2015In: Secure IT Systems: 20th Nordic Conference, NordSec 2015, Stockholm, Sweden, October 19–21, 2015, Proceedings, Springer, 2015, Vol. 9417, p. 191-196Conference paper (Refereed)
    Abstract [en]

    Firewalls are essential security devices that can provide protection against network attacks. To be effective, a firewall must be properly configured to ensure consistency with the security policy. However, configuring is a complex and error-prone process. This work tries to identify the reasons behind firewall misconfigurations. To achieve our goal, we conducted a series of semi-structured interviews with system administrators that manage access control lists in networks of different sizes. The paper discusses our interview results and describes future work.

  • 108.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Koewer, Richard
    FH Campus Wien, Austria.
    Mulazzani, Martin
    SBA Research, Austria.
    Huber, Markus
    SBA Research, Austria.
    Schrittwieser, Sebastian
    SBA Research, Austria.
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Weippl, Edgar
    SBA Research, Austria.
    Spoiled Onions: Exposing Malicious Tor Exit Relays2014In: Privacy Enhancing Technologies, Springer, 2014, p. 304-331Conference paper (Refereed)
    Abstract [en]

    Tor exit relays are operated by volunteers and together push more than 1 GiB/s of network traffic. By design, these volunteers are able to inspect and modify the anonymized network traffic. In this paper, we seek to expose such malicious exit relays and document their actions. First, we monitored the Tor network after developing two fast and modular exit relay scanners-one for credential sniffing and one for active MitM attacks. We implemented several scanning modules for detecting common attacks and used them to probe all exit relays over a period of several months. We discovered numerous malicious exit relays engaging in a multitude of different attacks. To reduce the attack surface users are exposed to, we patched Torbutton, an existing browser extension and part of the Tor Browser Bundle, to fetch and compare suspicious X. 509 certificates over independent Tor circuits. Our work makes it possible to continuously and systematically monitor Tor exit relays. We are able to detect and thwart many man-in-the-middle attacks, thereby making the network safer for its users. All our source code is available under a free license.

  • 109.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    How China Is Blocking Tor2012Report (Other academic)
    Abstract [en]

    Not only the free web is victim to China’s excessive censorship, but also the Tor anonymity network: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the blocking mechanism is implemented, we conjecture how China’s Tor blocking infrastructure is designed and we propose countermeasures. Our work bolsters the understanding of China’s censorship capabilities and thus paves the way towards more effective evasion techniques.

  • 110.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    How the Great Firewall of China is Blocking Tor2012Conference paper (Refereed)
    Abstract [en]

    Internet censorship in China is not just limited to the web: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the blocking mechanism is implemented, we conjecture how China's Tor blocking infrastructure is designed and we propose circumvention techniques. Our work bolsters the understanding of China's censorship capabilities and thus paves the way towards more effective circumvention techniques.

  • 111.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Spoiled Onions: Exposing Malicious Tor Exit Relays2014Report (Other academic)
    Abstract [en]

    Several hundred Tor exit relays together push more than 1 GiB/s of network traffic. However, it iseasy for exit relays to snoop and tamper with anonymised network traffic and as all relays are runby independent volunteers, not all of them are innocuous.

    In this paper, we seek to expose malicious exit relays and document their actions. First, wemonitored the Tor network after developing a fast and modular exit relay scanner. We implementedseveral scanning modules for detecting common attacks and used them to probe all exit relays over aperiod of four months. We discovered numerous malicious exit relays engaging in different attacks.To reduce the attack surface users are exposed to, we further discuss the design and implementationof a browser extension patch which fetches and compares suspicious X.509 certificates overindependent Tor circuits.

    Our work makes it possible to continuously monitor Tor exit relays. We are able to detect andthwart many man-in-the-middle attacks which makes the network safer for its users. All our code isavailable under a free license.

123 101 - 111 of 111
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