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152
Low-Resource Routing Attacks Against Tor
, 2007
"... Tor has become one of the most popular overlay networks for anonymizing TCP traffic. Its popularity is due in part to its perceived strong anonymity properties and its relatively low latency service. Low latency is achieved through Tor’s ability to balance the traffic load by optimizing Tor router s ..."
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Cited by 104 (14 self)
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Tor has become one of the most popular overlay networks for anonymizing TCP traffic. Its popularity is due in part to its perceived strong anonymity properties and its relatively low latency service. Low latency is achieved through Tor’s ability to balance the traffic load by optimizing Tor router selection to probabilistically favor routers with highbandwidth capabilities. We investigate how Tor’s routing optimizations impact its ability to provide strong anonymity. Through experiments conducted on PlanetLab, we show the extent to which routing performance optimizations have left the system vulnerable to end-to-end traffic analysis attacks from non-global adversaries with minimal resources. Further, we demonstrate that entry guards, added to mitigate path disruption attacks, are themselves vulnerable to attack. Finally, we explore solutions to improve Tor’s current routing algorithms and propose alternative routing strategies that prevent some of the routing attacks used in our experiments.
Hot or not: Revealing hidden services by their clock skew
- In 13th ACM Conference on Computer and Communications Security (CCS 2006
, 2006
"... Location-hidden services, as offered by anonymity systems such as Tor, allow servers to be operated under a pseudonym. As Tor is an overlay network, servers hosting hidden services are accessible both directly and over the anonymous channel. Traffic patterns through one channel have observable effec ..."
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Cited by 101 (3 self)
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Location-hidden services, as offered by anonymity systems such as Tor, allow servers to be operated under a pseudonym. As Tor is an overlay network, servers hosting hidden services are accessible both directly and over the anonymous channel. Traffic patterns through one channel have observable effects on the other, thus allowing a service’s pseudonymous identity and IP address to be linked. One proposed solution to this vulnerability is for Tor nodes to provide fixed quality of service to each connection, regardless of other traffic, thus reducing capacity but resisting such interference attacks. However, even if each connection does not influence the others, total throughput would still affect the load on the CPU, and thus its heat output. Unfortunately for anonymity, the result of temperature on clock skew can be remotely detected through observing timestamps. This attack works because existing abstract models of anonymitynetwork nodes do not take into account the inevitable imperfections of the hardware they run on. Furthermore, we suggest the same technique could be exploited as a classical covert channel and can even provide geolocation.
Shining light in dark places: Understanding the Tor network
- In Proceedings of the 8th Privacy Enhancing Technologies Symposium
, 2008
"... Abstract. To date, there has yet to be a study that characterizes the usage of a real deployed anonymity service. We present observations and analysis obtained by participating in the Tor network. Our primary goals are to better understand Tor as it is deployed and through this understanding, propos ..."
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Cited by 92 (19 self)
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Abstract. To date, there has yet to be a study that characterizes the usage of a real deployed anonymity service. We present observations and analysis obtained by participating in the Tor network. Our primary goals are to better understand Tor as it is deployed and through this understanding, propose improvements. In particular, we are interested in answering the following questions: (1) How is Tor being used? (2) How is Tor being mis-used? (3) Who is using Tor? To sample the results, we show that web traffic makes up the majority of the connections and bandwidth, but non-interactive protocols consume a disproportionately large amount of bandwidth when compared to interactive protocols. We provide a survey of how Tor is being misused, both by clients and by Tor router operators. In particular, we develop a method for detecting exit router logging (in certain cases). Finally, we present evidence that Tor is used throughout the world, but router participation is limited to only a few countries. 1
Sampled traffic analysis by internet-exchange-level adversaries
- In Privacy Enhancing Technologies (PET), LNCS
, 2007
"... Abstract. Existing low-latency anonymity networks are vulnerable to traffic analysis, so location diversity of nodes is essential to defend against attacks. Previous work has shown that simply ensuring geographical diversity of nodes does not resist, and in some cases exacerbates, the risk of traffi ..."
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Cited by 83 (4 self)
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Abstract. Existing low-latency anonymity networks are vulnerable to traffic analysis, so location diversity of nodes is essential to defend against attacks. Previous work has shown that simply ensuring geographical diversity of nodes does not resist, and in some cases exacerbates, the risk of traffic analysis by ISPs. Ensuring high autonomous-system (AS) diversity can resist this weakness. However, ISPs commonly connect to many other ISPs in a single location, known as an Internet eXchange (IX). This paper shows that IXes are a single point where traffic analysis can be performed. We examine to what extent this is true, through a case study of Tor nodes in the UK. Also, some IXes sample packets flowing through them for performance analysis reasons, and this data could be exploited to de-anonymize traffic. We then develop and evaluate Bayesian traffic analysis techniques capable of processing this sampled data. 1
How much anonymity does network latency leak
- In CCS ’07: Proceedings of the 14th ACM conference on Computer and communications security. ACM
, 2007
"... Low-latency anonymity systems such as Tor, AN.ON, Crowds, and Anonymizer.com aim to provide anonymous connections that are both untraceable by “local ” adversaries who control only a few machines, and have low enough delay to support anonymous use of network services like web browsing and remote log ..."
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Cited by 76 (1 self)
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Low-latency anonymity systems such as Tor, AN.ON, Crowds, and Anonymizer.com aim to provide anonymous connections that are both untraceable by “local ” adversaries who control only a few machines, and have low enough delay to support anonymous use of network services like web browsing and remote login. One consequence of these goals is that these services leak some information about the network latency between the sender and one or more nodes in the system. We present two attacks on low-latency anonymity schemes using this information. The first attack allows a pair of colluding web sites to predict, based on local timing information and with no additional resources, whether two connections from the same Tor exit node are using the same circuit with high confidence. The second attack requires more resources but allows a malicious website to gain several bits of information about a client each time he visits the site. We evaluate both attacks against two low-latency anonymity protocols – the Tor network and the MultiProxy proxy aggregator service – and conclude that both are highly vulnerable to these attacks. Categories and Subject Descriptors: C.2.0 [Computer Networks]: General—Security and protection;
Timing analysis in low-latency mix networks: attacks and defenses
- IN: PROCEEDINGS OF ESORICS
, 2006
"... Mix networks are a popular mechanism for anonymous Internet communications. By routing IP traffic through an overlay chain of mixes, they aim to hide the relationship between its origin and destination. Using a realistic model of interactive Internet traffic, we study the problem of defending low-la ..."
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Cited by 56 (0 self)
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Mix networks are a popular mechanism for anonymous Internet communications. By routing IP traffic through an overlay chain of mixes, they aim to hide the relationship between its origin and destination. Using a realistic model of interactive Internet traffic, we study the problem of defending low-latency mix networks against attacks based on correlating inter-packet intervals on two or more links of the mix chain. We investigate several attack models, including an active attack which involves adversarial modification of packet flows in order to “fingerprint” them, and analyze the tradeoffs between the amount of cover traffic, extra latency, and anonymity properties of the mix network. We demonstrate that previously proposed defenses are either ineffective, or impose a prohibitively large latency and/or bandwidth overhead on communicating applications. We propose a new defense based on adaptive padding.
Website fingerprinting in onion routing based anonymization networks
- in Proceedings of the 18th ACM Computer and Communications Security (ACM CCS) Workshop on Privacy in the Electronic Society (WPES 2011
, 2011
"... Low-latency anonymization networks such as Tor and JAP claim to hide the recipient and the content of communications from a local observer, i.e., an entity that can eavesdrop the traffic between the user and the first anonymization node. Especially users in totalitarian regimes strongly depend on su ..."
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Cited by 51 (1 self)
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Low-latency anonymization networks such as Tor and JAP claim to hide the recipient and the content of communications from a local observer, i.e., an entity that can eavesdrop the traffic between the user and the first anonymization node. Especially users in totalitarian regimes strongly depend on such networks to freely communicate. For these people, anonymity is particularly important and an analysis of the anonymization methods against various attacks is necessary to ensure adequate protection. In this paper we show that anonymity in Tor and JAP is not as strong as expected so far and cannot resist website fingerprinting attacks under certain circumstances. We first define features for website fingerprinting solely based on volume, time, and direction of the traffic. As a result, the subsequent classification becomes much easier. We apply support vector machines with the introduced features. We are able to improve recognition results of existing works on a given state-of-the-art dataset in Tor from 3 % to 55 % and in JAP from 20 % to 80%. The datasets assume a closed-world with 775 websites only. In a next step, we transfer our findings to a more complex and realistic open-world scenario, i.e., recognition of several websites in a set of thousands of random unknown websites. To the best of our knowledge, this work is the first successful attack in the open-world scenario. We achieve a surprisingly high true positive rate of up to 73 % for a false positive rate of 0.05%. Finally, we show preliminary results of a proof-of-concept implementation that applies camouflage as a countermeasure to hamper the fingerprinting attack. For JAP, the detection rate decreases from 80 % to 4 % and for Tor it drops from 55 % to about 3%.
S.: Performance Improvements on Tor or, Why Tor is Slow and What We’re Going to Do about It. http://www.torproject.org/press
, 2009
"... As Tor’s user base has grown, the performance of the Tor network has suffered. This document describes our current understanding of why Tor is slow, and lays out our options for fixing it. Over the past few years, our funding (and thus our development effort) has focused on usability and blocking-re ..."
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Cited by 42 (0 self)
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As Tor’s user base has grown, the performance of the Tor network has suffered. This document describes our current understanding of why Tor is slow, and lays out our options for fixing it. Over the past few years, our funding (and thus our development effort) has focused on usability and blocking-resistance. We’ve come up with a portable self-contained Windows bundle; deployed tools to handle the upcoming censorship arms race; further developed supporting applications like Vidalia, Torbutton, and Thandy; made it easier for users to be relays by adding better rate limiting and an easy graphical interface with uPnP support; developed an effective translation and localization team and infrastructure; and spread understanding of Tor in a safe word-of-mouth way that stayed mostly under the radar of censors. In parallel to adding these features, we’ve also been laying the groundwork for performance improve-ments. We’ve been working with academics to write research papers on improving Tor’s speed, funding some academic groups directly to come up with prototypes, and thinking hard about how to safely collect metrics about network performance. But it’s becoming increasingly clear that we’re not going to produce the perfect answers just by thinking hard. We need to roll out some attempts at solutions, and use the experience to get better intuition about how to really solve the problems. We’ve identified six main reasons why the Tor network is slow. Problem #1 is that Tor’s congestion
Traveling the Silk Road: A measurement analysis of a large anonymous online marketplace
"... We perform a comprehensive measurement analysis of Silk Road, an anonymous, international online marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We gather and analyze data over eight months between the end of 2011 and 2012, including daily crawls of the m ..."
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Cited by 40 (6 self)
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We perform a comprehensive measurement analysis of Silk Road, an anonymous, international online marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We gather and analyze data over eight months between the end of 2011 and 2012, including daily crawls of the marketplace for nearly six months in 2012. We obtain a detailed picture of the type of goods being sold on Silk Road, and of the revenues made both by sellers and Silk Road operators. Through examining over 24,400 separate items sold on the site, we show that Silk Road is overwhelmingly used as a market for controlled substances and narcotics, and that most items sold are available for less than three weeks. The majority of sellers disappears within roughly three months of their arrival, but a core of 112 sellers has been present throughout our measurement interval. We evaluate the total revenue made by all sellers, from public listings, to slightly over USD 1.2 million per month; this corresponds to about USD 92,000 per month in commissions for the Silk Road operators. We further show that the marketplace has been operating steadily, with daily sales and number of sellers overall increasing over our measurement interval. We discuss economic and policy implications of our analysis and results, including ethical considerations for future research in this area.
AS-awareness in Tor Path Selection
"... Tor is an anonymous communications network with thousands of router nodes worldwide. An intuition reflected in much of the literature on anonymous communications is that, as an anonymity network grows, it becomes more secure against a given observer because the observer will see less of the network. ..."
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Cited by 39 (6 self)
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Tor is an anonymous communications network with thousands of router nodes worldwide. An intuition reflected in much of the literature on anonymous communications is that, as an anonymity network grows, it becomes more secure against a given observer because the observer will see less of the network. In particular, as the Tor network grows from volunteers operating relays all over the world, it becomes less and less likely for a single autonomous system (AS) to be able to observe both ends of an anonymous connection. Yet, as the network continues to grow significantly, no analysis has been done to determine if this intuition is correct. Further, modifications to Tor’s path selection algorithm to help clients avoid an AS-level observer have not been proposed and analyzed.
