@misc{MitsevaPanchenkoLanzeetal., author = {Mitseva, Asya and Panchenko, Andriy and Lanze, Fabian and Henze, Martin and Engel, Thomas and Wehrle, Klaus}, title = {POSTER: Fingerprinting Tor Hidden Services}, series = {In Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS '16). Association for Computing Machinery, New York, NY, USA}, journal = {In Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS '16). Association for Computing Machinery, New York, NY, USA}, publisher = {ACM}, address = {New York}, isbn = {978-1-4503-4139-4}, doi = {10.1145/2976749.2989054}, pages = {1766 -- 1768}, language = {en} } @inproceedings{PanchenkoMitsevaHenzeetal., author = {Panchenko, Andriy and Mitseva, Asya and Henze, Martin and Lanze, Fabian and Engel, Thomas and Wehrle, Klaus}, title = {Analysis of Fingerprinting Techniques for Tor Hidden Services}, series = {WPES '17 Proceedings of the 2017 on Workshop on Privacy in the Electronic Society, Dallas, Texas, USA, October 2017}, booktitle = {WPES '17 Proceedings of the 2017 on Workshop on Privacy in the Electronic Society, Dallas, Texas, USA, October 2017}, publisher = {ACM}, address = {New York, NY}, isbn = {978-1-4503-5175-1}, doi = {10.1145/3139550.3139564}, pages = {165 -- 175}, language = {en} } @misc{MitsevaPanchenkoEngel, author = {Mitseva, Asya and Panchenko, Andriy and Engel, Thomas}, title = {The state of affairs in BGP security: A survey of attacks and defenses}, series = {Computer Communications}, volume = {124}, journal = {Computer Communications}, issn = {0140-3664}, doi = {10.1016/j.comcom.2018.04.013}, pages = {45 -- 60}, language = {en} } @misc{PennekampHillerReuteretal., author = {Pennekamp, Jan and Hiller, Jens and Reuter, Sebastian and De la Cadena, Wladimir and Mitseva, Asya and Henze, Martin and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {Multipathing Traffic to Reduce Entry Node Exposure in Onion Routing}, series = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (Poster) (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, journal = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (Poster) (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, publisher = {IEEE Press}, isbn = {978-1-7281-2700-2}, issn = {2643-3303}, doi = {10.1109/ICNP.2019.8888029}, pages = {2}, abstract = {Users of an onion routing network, such as Tor, depend on its anonymity properties. However, especially malicious entry nodes, which know the client's identity, can also observe the whole communication on their link to the client and, thus, conduct several de-anonymization attacks. To limit this exposure and to impede corresponding attacks, we propose to multipath traffic between the client and the middle node to reduce the information an attacker can obtain at a single vantage point. To facilitate the deployment, only clients and selected middle nodes need to implement our approach, which works transparently for the remaining legacy nodes. Furthermore, we let clients control the splitting strategy to prevent any external manipulation.}, language = {en} } @misc{DeLaCadenaMitsevaPennekampetal., author = {De La Cadena, Wladimir and Mitseva, Asya and Pennekamp, Jan and Hiller, Jens and Lanze, Fabian and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {POSTER: Traffic Splitting to Counter Website Fingerprinting}, series = {CCS '19 Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security , London, UK, November 11 - 15, 2019.}, journal = {CCS '19 Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security , London, UK, November 11 - 15, 2019.}, publisher = {ACM Press}, address = {New York}, isbn = {978-1-4503-6747-9}, doi = {10.1145/3319535.3363249}, pages = {2533 -- 2535}, abstract = {Website fingerprinting (WFP) is a special type of traffic analysis, which aims to infer the websites visited by a user. Recent studies have shown that WFP targeting Tor users is notably more effective than previously expected. Concurrently, state-of-the-art defenses have been proven to be less effective. In response, we present a novel WFP defense that splits traffic over multiple entry nodes to limit the data a single malicious entry can use. Here, we explore several traffic-splitting strategies to distribute user traffic. We establish that our weighted random strategy dramatically reduces the accuracy from nearly 95\% to less than 35\% for four state-of-the-art WFP attacks without adding any artificial delays or dummy traffic.}, language = {en} } @misc{DelaCadenaKaiserMitsevaetal., author = {De la Cadena, Wladimir and Kaiser, Daniel and Mitseva, Asya and Panchenko, Andriy and Engel, Thomas}, title = {Analysis of Multi-path Onion Routing-based Anonymization Networks}, series = {Data and Applications Security and Privacy XXXIII : 33rd Annual IFIP WG 11.3 Conference, DBSec 2019, Charleston, SC, USA, July 15-17, 2019, Proceedings}, journal = {Data and Applications Security and Privacy XXXIII : 33rd Annual IFIP WG 11.3 Conference, DBSec 2019, Charleston, SC, USA, July 15-17, 2019, Proceedings}, editor = {Foley, Simon N.}, publisher = {Springer}, address = {Frankfurt am Main}, isbn = {978-3-030-22478-3}, issn = {0302-9743}, doi = {10.1007/978-3-030-22479-0_13}, pages = {240 -- 258}, language = {en} } @misc{MitsevaEngelPanchenko, author = {Mitseva, Asya and Engel, Thomas and Panchenko, Andriy}, title = {Analyzing PeerFlow - A Bandwidth Estimation System for Untrustworthy Environments}, series = {Sicherheit 2020 : Sicherheit, Schutz und Zuverl{\"a}ssigkeit ; Konferenzband der 10. Jahrestagung des Fachbereichs Sicherheit der Gesellschaft f{\"u}r Informatik e.V. (GI) ; 17.- 20. M{\"a}rz 2020 in G{\"o}ttingen}, journal = {Sicherheit 2020 : Sicherheit, Schutz und Zuverl{\"a}ssigkeit ; Konferenzband der 10. Jahrestagung des Fachbereichs Sicherheit der Gesellschaft f{\"u}r Informatik e.V. (GI) ; 17.- 20. M{\"a}rz 2020 in G{\"o}ttingen}, editor = {Reinhardt, Delphine and Langweg, Hanno and Witt, Bernhard C. and Fischer, Mathias}, publisher = {Gesellschaft f{\"u}r Informatik}, address = {Bonn}, isbn = {978-3-88579-695-4}, doi = {10.18420/sicherheit2020_02}, pages = {29 -- 40}, language = {en} } @misc{MitsevaAleksandrovaEngeletal., author = {Mitseva, Asya and Aleksandrova, Marharyta and Engel, Thomas and Panchenko, Andriy}, title = {Security and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor}, series = {ICT Systems Security and Privacy Protection : 35th IFIP TC 11 International Conference, SEC 2020, Maribor, Slovenia, September 21-23, 2020}, journal = {ICT Systems Security and Privacy Protection : 35th IFIP TC 11 International Conference, SEC 2020, Maribor, Slovenia, September 21-23, 2020}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-58201-2}, issn = {1868-4238}, doi = {10.1007/978-3-030-58201-2_15}, pages = {219 -- 233}, language = {en} } @misc{DelaCadenaMitsevaHilleretal., author = {De la Cadena, Wladimir and Mitseva, Asya and Hiller, Jens and Pennekamp, Jan and Reuter, Sebastian and Filter, Julian and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {TrafficSliver: Fighting Website Fingerprinting Attacks with Traffic Splitting}, series = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, journal = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, publisher = {Association for Computing Machinery}, address = {New York}, isbn = {978-1-4503-7089-9}, doi = {10.1145/3372297.3423351}, pages = {1971 -- 1985}, abstract = {Website fingerprinting (WFP) aims to infer information about the content of encrypted and anonymized connections by observing patterns of data flows based on the size and direction of packets. By collecting traffic traces at a malicious Tor entry node — one of the weakest adversaries in the attacker model of Tor — a passive eavesdropper can leverage the captured meta-data to reveal the websites visited by a Tor user. As recently shown, WFP is significantly more effective and realistic than assumed. Concurrently, former WFP defenses are either infeasible for deployment in real-world settings or defend against specific WFP attacks only. To limit the exposure of Tor users to WFP, we propose novel lightweight WFP defenses, TrafficSliver, which successfully counter today's WFP classifiers with reasonable bandwidth and latency overheads and, thus, make them attractive candidates for adoption in Tor. Through user-controlled splitting of traffic over multiple Tor entry nodes, TrafficSliver limits the data a single entry node can observe and distorts repeatable traffic patterns exploited by WFP attacks.We first propose a network-layer defense, in which we apply the concept of multipathing entirely within the Tor network. We show that our network-layer defense reduces the accuracy from more than 98\% to less than 16\% for all state-of-the-art WFP attacks without adding any artificial delays or dummy traffic. We further suggest an elegant client-side application-layer defense, which is independent of the underlying anonymization network. By sending single HTTP requests for different web objects over distinct Tor entry nodes, our application-layer defense reduces the detection rate of WFP classifiers by almost 50 percentage points. Although it offers lower protection than our network-layer defense, it provides a security boost at the cost of a very low implementation overhead and is fully compatible with today's Tor network.}, language = {en} } @misc{MitsevaPennekampLohmoelleretal., author = {Mitseva, Asya and Pennekamp, Jan and Lohm{\"o}ller, Johannes and Ziemann, Torsten and Hoerchner, Carl and Wehrle, Klaus and Panchenko, Andriy}, title = {POSTER: How Dangerous is My Click? Boosting Website Fingerprinting By Considering Sequences of Webpages}, series = {Proceedings of the 28th ACM Conference on Computer and Communications Security (ACM CCS 2021), Seoul, Virtual Event, South Korea, November 2021}, journal = {Proceedings of the 28th ACM Conference on Computer and Communications Security (ACM CCS 2021), Seoul, Virtual Event, South Korea, November 2021}, publisher = {ACM Press}, address = {New York}, isbn = {978-1-4503-8454-4}, doi = {10.1145/3460120.3485347}, pages = {2411 -- 2413}, language = {en} } @misc{PanchenkoMitsevaKnabe, author = {Panchenko, Andriy and Mitseva, Asya and Knabe, Sara}, title = {WhisperChord: Scalable and Secure Node Discovery for Overlay Networks}, series = {IEEE 46th Conference on Local Computer Networks (LCN), Edmonton, AB, Canada , 4-7 Oct. 2021}, journal = {IEEE 46th Conference on Local Computer Networks (LCN), Edmonton, AB, Canada , 4-7 Oct. 2021}, publisher = {IEEE}, isbn = {978-1-6654-1886-7}, issn = {0742-1303}, doi = {10.1109/LCN52139.2021.9525008}, pages = {170 -- 177}, abstract = {Node discovery is a fundamental service for any overlay network, including anonymization networks. Although anonymization and node discovery are two disjoint services, the node discovery has a direct impact on the anonymization. Centralized methods require a trusted third party, limit the network scalability, and are vulnerable to intersection (statistical disclosure) attacks. Therefore, several distributed node discovery methods were proposed to meet the security requirements of anonymization networks through additional structures within Distributed Hash Tables (DHTs). However, they require a high management overhead, a strict cooperation between nodes, and are susceptible to active and passive attacks.We propose WhisperChord—an alternative distributed node discovery approach, which incorporates gossiping into structured overlays. WhisperChord is based on a Chord DHT and neither creates any additional structures within the DHT nor requires any trusted third party. Via simulations, we show that our method provides superior protection against active attacks than prior methods and can effectively thwart information leakages.}, language = {en} } @misc{PanchenkoMitsevaZiemannetal., author = {Panchenko, Andriy and Mitseva, Asya and Ziemann, Torsten and Hering, Till}, title = {GuardedGossip: Secure and Anonymous Node Discovery in Untrustworthy Networks}, series = {Security and Privacy in Communication Networks : 17th EAI International Conference, SecureComm 2021, Virtual Event, September 6-9, 2021, Proceedings, Part I}, journal = {Security and Privacy in Communication Networks : 17th EAI International Conference, SecureComm 2021, Virtual Event, September 6-9, 2021, Proceedings, Part I}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-90018-2}, issn = {1867-8211}, doi = {10.1007/978-3-030-90019-9_7}, pages = {123 -- 143}, abstract = {Node discovery is a fundamental service for any overlay network. It is a particular challenge to provide unbiased discovery in untrustworthy environments, e.g., anonymization networks. Although a major line of research focused on solving this problem, proposed methods have been shown to be vulnerable either to active attacks or to leak routing information, both threatening the anonymity of users. In response, we propose GuardedGossip—a novel gossip-based node discovery protocol—that achieves an unbiased random node discovery in a fully-decentralized and highly-scalable fashion. It is built on top of a Chord distributed hash table (DHT) and relies on witness nodes and bound checks to resist active attacks. To limit routing information leakages, GuardedGossip uses gossiping to create uncertainty in the process of node discovery. By incorporating the principles of DHTs with the unstructured nature of gossiping in a subtle way, we profit from the strengths of both techniques while carefully mitigating their shortcomings. We show that GuardedGossip provides a sufficient level of security for users even if 20\% of the participating nodes are malicious. Concurrently, our system scales gracefully and provides an adequate overhead for its security and privacy benefits.}, language = {en} } @misc{MitsevaPanchenko, author = {Mitseva, Asya and Panchenko, Andriy}, title = {Stop, don't click here anymore: boosting website fingerprinting by considering sets of subpages}, series = {Proceedings of the 33rd USENIX Security Symposium (USENIX Sec 2024), Philadelphia, PA, USA, August 14-16, 2024}, journal = {Proceedings of the 33rd USENIX Security Symposium (USENIX Sec 2024), Philadelphia, PA, USA, August 14-16, 2024}, isbn = {978-1-939133-44-1}, pages = {4139 -- 4156}, abstract = {A type of traffic analysis, website fingerprinting (WFP), aims to reveal the website a user visits over an encrypted and anonymized connection by observing and analyzing data flow patterns. Its efficiency against anonymization networks such as Tor has been widely studied, resulting in methods that have steadily increased in both complexity and power. While modern WFP attacks have proven to be highly accurate in laboratory settings, their real-world feasibility is highly debated. These attacks also exclude valuable information by ignoring typical user browsing behavior: users often visit multiple pages of a single website sequentially, e.g., by following links. In this paper, we aim to provide a more realistic assessment of the degree to which Tor users are exposed to WFP. We propose both a novel WFP attack and efficient strategies for adapting existing methods to account for sequential visits of pages within a website. While existing WFP attacks fail to detect almost any website in real-world settings, our novel methods achieve F1-scores of 1.0 for more than half of the target websites. Our attacks remain robust against state-of- the-art WFP defenses, achieving 2.5 to 5 times the accuracy of prior work, and in some cases even rendering the defenses useless. Our methods enable to estimate and to communicate to the user the risk of successive page visits within a website (even in the presence of noise pages) to stop before the WFP attack reaches a critical level of confidence.}, language = {en} } @misc{MitsevaAlexandrovaPanchenko, author = {Mitseva, Asya and Alexandrova, Marharyta and Panchenko, Andriy}, title = {Security and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor}, series = {Computers and Security}, volume = {132}, journal = {Computers and Security}, issn = {1872-6208}, doi = {10.1016/j.cose.2023.103374}, abstract = {Tor is the most popular anonymization network with millions of daily users. This makes it an attractive target for attacks, e.g., by malicious autonomous systems (ASs) performing active routing attacks to become man in the middle and deanonymize users. It was shown that the number of such malicious ASs is significantly larger than previously expected due to the lack of security guarantees in the Border Gateway Protocol (BGP). In response, recent works suggest alternative Tor path selection methods preferring Tor nodes with higher resilience to active BGP attacks. In this work, we analyze the implications of such proposals and demonstrate that two state-of-the-art path selection methods, namely Counter-RAPTOR and DPSelect, are not as secure as thought before. First, we show that DPSelect achieves only one third of its originally claimed resilience and, thus, is not as resilient as widely accepted. Second, we reveal that the resilience to active BGP attacks on the way back, i.e., from the first anonymization node to a given Tor user, provided by both methods is significantly lower than on the forward path. Beside their lower resilience in specific cases, we show that for particular users the usage of Counter-RAPTOR and DPSelect also leads to leakage of user's location. Furthermore, we uncover the performance implications of both methods and identify scenarios where their usage leads to significant performance bottlenecks. Finally, we propose a new metric to quantify the user's location leakage by path selection. Using this metric and performing large-scale analysis, we show to which extent a malicious Tor middle node can fingerprint the user's location and the confidence it can achieve. Our findings shed light on the implications of path selection methods on the users' anonymity and the need for further research.}, language = {en} } @misc{MitsevaThierseHoffmannetal., author = {Mitseva, Asya and Thierse, Paul and Hoffmann, Harald and Er, Devran and Panchenko, Andriy}, title = {Challenges and Pitfalls in Generating Representative ICS Datasets in Cyber Security Research}, series = {Computer Security, ESORICS 2022 International Workshops CyberICPS 2022, SECPRE 2022, SPOSE 2022, CPS4CIP 2022, CDT\&SECOMANE 2022, EIS 2022, and SecAssure 2022 Copenhagen, Denmark, September 26-30, 2022, Revised Selected Papers}, journal = {Computer Security, ESORICS 2022 International Workshops CyberICPS 2022, SECPRE 2022, SPOSE 2022, CPS4CIP 2022, CDT\&SECOMANE 2022, EIS 2022, and SecAssure 2022 Copenhagen, Denmark, September 26-30, 2022, Revised Selected Papers}, editor = {Katsikas, Sokratis}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-031-25459-8}, doi = {10.1007/978-3-031-25460-4_22}, pages = {379 -- 397}, language = {en} } @phdthesis{Mitseva, author = {Mitseva, Asya}, title = {State of affairs in online user privacy : assessing real-world user information leakages and designing effective and practical countermeasures}, publisher = {Brandenburgische Technische Universit{\"a}t}, address = {Cottbus-Senftenberg}, doi = {10.26127/BTUOpen-7214}, pages = {xxvii, 194}, abstract = {The Tor network ensures confidentiality of user data over the Internet and hides the IP addresses and relationships between communication partners to avoid user profiling and censorship. However, Tor cannot hide the number, direction, and timing of transmitted packets. Two types of attackers - autonomous systems (AS) and malicious Tor nodes - can exploit this for sophisticated attacks, such as website fingerprinting (WFP) and end-to-end traffic correlation, or fingerprinting attacks revealing the Tor users' location. On the other hand, in case of a malicious first Tor node or a malicious AS on the path between the user and the Tor network, the scalability of prior WFP attacks remains questionable due to impractical assumptions. This dissertation aims to provide a more realistic assessment of the exposure of Tor users to passive deanonymization attacks from different perspectives. First, we conduct a comprehensive review of fundamental Border Gateway Protocol (BGP) threats. We present a methodology for evaluating existing BGP security proposals and provide an extensive and up-to-date survey of proposals intended to make BGP secure and methods for detecting and mitigating routing instabilities. Based on the identified research gaps and unresolved challenges, we analyze the current level of resilience of Tor and two alternative Tor path selection methods against malicious ASs. While we detect a notable increase in the Tor's resilience to BGP attacks over the years, when measured from a Tor user to its first Tor node, the resilience provided by the alternative path selection methods on the way back, i.e., from the first Tor node to a Tor user, has decreased notably compared to the resilience measured on the forward path for these methods. Moreover, these methods tend to select first Tor nodes in a predictable manner, resulting in the exposure of users' locations to Tor middle nodes. We also show novel attacks against a state-of-the-art method for measuring bandwidth capabilities of Tor nodes, allowing a low-bandwidth attacker to gain notably higher bandwidth estimates than theoretically defined. We propose a novel lightweight defense against malicious Tor nodes, performing WFP or end-to-end traffic correlation, that splits user traffic over multiple Tor paths. Our defense is fully implemented on the user side, reducing deployment costs and making it independent of the underlying anonymization network. We also propose a metric that is capable of quantifying the user's location leakage considering a malicious Tor middle node. This metric enables Tor users to avoid specific first Tor nodes by strategically selecting those from which their location cannot be revealed. Finally, we examine the real-world scalability of WFP, especially against Tor users who visit several pages of a single website consecutively. We propose both a novel WFP attack and efficient strategies for adapting existing methods to account for sequential visits of pages within a website.}, language = {en} } @misc{MitsevaLewandowskyPanchenko, author = {Mitseva, Asya and Lewandowsky, Marco and Panchenko, Andriy}, title = {Poster: characterization of dominant and specific network patterns in industrial control systems}, series = {2025 23rd International Symposium on Network Computing and Applications (NCA)}, journal = {2025 23rd International Symposium on Network Computing and Applications (NCA)}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {979-8-3315-7842-8}, doi = {10.1109/NCA67271.2025.00059}, pages = {314 -- 315}, abstract = {The increasing digitization and interconnection of Industrial Control Systems (ICS) to the Internet render them susceptible to cyber attacks. Thus, a major line of research focuses on the design of reactive security solutions in the form of industrial intrusion detection systems, which aim to detect anomalies in a normal system operation. However, a crucial prerequisite for the accurate detection and localization of anomalies is the identification of typical traffic patterns that are exclusive to characterize the normal ICS behavior. Unlike previous work focusing on complex and protocol-dependent models, for characterizing ICS network traffic, in this work we propose simple, easy deployable, and effective rules for determining whether ICS network traffic, unlike traditional IT networks, remains stable over time. The main advantage of our rules is that they can be used to estimate the time required to identify the most dominant ICS traffic patterns in a given ICS. We show the efficacy of our rules by analyzing multiple ICS datasets with different industrial network protocols.}, language = {en} }