Ústav informačních systémů


Recent Submissions

Now showing 1 - 5 of 6
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    DNS over HTTPS Detection Using Standard Flow Telemetry
    (IEEE, 2023-01-31) Jeřábek, Kamil; Hynek, Karel; Ryšavý, Ondřej; Burgetová, Ivana
    The aim of DNS over HTTPS (DoH) is to enhance users’ privacy by encrypting DNS. However, it also enables adversaries to bypass security mechanisms that rely on inspecting unencrypted DNS. Therefore in some networks, it is crucial to detect and block DoH to maintain security. Unfortunately, DoH is particularly challenging to detect, because it is designed to blend into regular HTTPS traffic. So far, there have been numerous proposals for DoH detection; however, they rely on specialized flow monitoring software that can export complex features that cannot be often computed on the running sequence or suffer from low accuracy. These properties significantly limit their mass deployment into real-world environments. Therefore this study proposes a novel DoH detector that uses IP-based, machine learning, and active probing techniques to detect DoH effectively with standard flow monitoring software. The use of classical flow features also enables its deployment in any network infrastructure with flow-monitoring appliances such as intelligent switches, firewalls, or routers. The proposed approach was tested using lab-created and real-world ISP-based network data and achieved a high classification accuracy of 0.999 and an F1 score of 0.998 with no false positives.
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    Comparison of Fungal Thermophilic and Mesophilic Catalase-Peroxidases for Their Antioxidative Properties
    (MDPI, 2023-07-04) Poljovka, Andrej; Musil, Miloš; Bednář, David; Chovanová, Katarína; Bauerová-Hlinková, Vladena; Bellová, Jana; Kohútová, Lenka; Baráth, Peter; Zámocký, Marcel
    Catalase-peroxidases (KatGs) are unique bifunctional oxidoreductases that contain heme in their active centers allowing both the peroxidatic and catalatic reaction modes. These originally bacterial enzymes are broadly distributed among various fungi allowing them to cope with reactive oxygen species present in the environment or inside the cells. We used various biophysical, biochemical, and bioinformatics methods to investigate differences between catalase-peroxidases originating in thermophilic and mesophilic fungi from different habitats. Our results indicate that the architecture of the active center with a specific post-translational modification is highly similar in mesophilic and thermophilic KatG and also the peroxidatic acitivity with ABTS, guaiacol, and L-DOPA. However, only the thermophilic variant CthedisKatG reveals increased manganese peroxidase activity at elevated temperatures. The catalatic activity releasing molecular oxygen is comparable between CthedisKatG and mesophilic MagKatG1 over a broad temperature range. Two constructed point mutations in the active center were performed selectively blocking the formation of described post-translational modification in the active center. They exhibited a total loss of catalatic activity and changes in the peroxidatic activity. Our results indicate the capacity of bifunctional heme enzymes in the variable reactivity for potential biotech applications.
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    Increasing Visibility of IEC 104 Communication in the Smart Grid
    (BCS Learning and Development Ltd., 2019-06-25) Matoušek, Petr; Ryšavý, Ondřej; Grégr, Matěj
    Energy systems like smart grids are part of critical infrastructure and their interruption or blackout may have fatal consequences on energy production, distribution, and eventually the life of individual people. In order to secure communication in Industrial Control Systems (ICS) and detect cyber attacks on smart grids, we need to increase visibility of ICS communication so that an operator can see what commands are sent between ICS devices. Security monitoring of ICS transmission requires (i) retrieving monitoring data from ICS packets, (ii) processing and analyzing extracted data, (iii) visualizing the passing communication to the operator. The  proposed work presents a concept of ICS flow monitoring system that extracts meta data from ICS packet headers and creates ICS flow records similarly to Netflow/IPFIX system. ICS flows represent communication in the smart grid network that is further visualized using dashboard and communication charts. Unlike traditional monitoring approach that works with network and transport layer data only, we extend flow monitoring to application layer with focus on ICS protocols. The proposed approach is demonstrated on monitoring IEC 60870-5-104 communication.
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    Responsible And Safe Home Metering: How to Design A Privacy-Friendly Metering System?
    (IGI Global, 2023-04-03) Polčák, Libor
    The European directive on energy efficiency requires that all meters in multi-apartment buildings installed after 25 October 2020 shall be remotely readable devices when technically feasible and cost-effective in terms of being proportionate to the potential energy savings. The European Commission Recommendation of 9 March 2012 on preparations for the roll-out of smart metering systems (2012/148/EU) explicitly mentions that smart metering predominantly processes personal data. This chapter recommends how to design a metering system that fully conforms to legal regulations. The main contribution is the recommendation of eight steps for data controllers that make metering systems legally compliant. Additionally, the chapter lists recommendations for smart meter manufacturers that remove the burden of being a controller of the processing. The recommendations apply to the distribution of electricity, water, gas, heat, cooling, and other energies. The chapter shows that the recommendations can be generalized for smart home deployments.
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    Metering Homes: Do Energy Efficiency and Privacy Need to be in Conflict?
    (SciTePress - Science and Technology Publications, 2022-07-11) Polčák, Libor; Matoušek, Petr
    The European directive on energy efficiency requires that all meters in multi-apartment buildings installed after 25 October 2020 shall be remotely readable devices where technically feasible and cost effective in terms of being proportionate in relation to the potential energy savings. In practise, this means that some manufacturers produce meters that monitor energy consumption in very short intervals, for example, less than two minutes; even though the directive expects to provide billing information to consumers only once a month starting from 2022. This paper reviews privacy and security risks stemming from the short readouts and provides recommendations for manufacturers and suppliers. The paper focuses on a Wireless M-Bus metering devices that we observed being sold and advertised as the solution to fulfill the European directive on energy efficiency requirements. Nevertheless, we believe that many recommendations and observations are applicable also to other protocols.