An ISP-Scale Deployment of Tapdance
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An ISP-Scale Deployment of Tapdance
An ISP-Scale Deployment of TapDance Sergey Frolov Fred Douglas Will Scott Eric Wustrow Google Allison McDonald University of Colorado Boulder Benjamin VanderSloot University of Michigan Rod Hynes Michalis Kallitsis David G. Robinson Adam Kruger Merit Network Upturn Psiphon Steve Schultze Nikita Borisov J. Alex Halderman Georgetown University Law University of Illinois University of Michigan Center ABSTRACT network operators, who provide censorship circumvention In this talk, we will report initial results from the world’s functionality for any connection that passes through their net- first ISP-scale field trial of a refraction networking system. works. To accomplish this, clients make HTTPS connections Refraction networking is a next-generation censorship cir- to sites that they can reach, where such connections traverse cumvention approach that locates proxy functionality in the a participating network. The participating network operator middle of the network, at participating ISPs or other network recognizes a steganographic signal from the client and ap- operators. We built a high-performance implementation of pends the user’s requested data to the encrypted connection the TapDance refraction networking scheme and deployed it response. From the perspective of the censor, these connec- on four ISP uplinks with an aggregate bandwidth of 100 Gbps. tions are indistinguishable from normal TLS connections to Over one week of operation, our deployment served more sites the censor has not blocked. To block the refraction con- than 50,000 real users. The experience demonstrates that nections, the censor would need to block all connections that TapDance can be practically realized at ISP scale with good traverse a participating network. -
Threat Modeling and Circumvention of Internet Censorship by David Fifield
Threat modeling and circumvention of Internet censorship By David Fifield A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Computer Science in the Graduate Division of the University of California, Berkeley Committee in charge: Professor J.D. Tygar, Chair Professor Deirdre Mulligan Professor Vern Paxson Fall 2017 1 Abstract Threat modeling and circumvention of Internet censorship by David Fifield Doctor of Philosophy in Computer Science University of California, Berkeley Professor J.D. Tygar, Chair Research on Internet censorship is hampered by poor models of censor behavior. Censor models guide the development of circumvention systems, so it is important to get them right. A censor model should be understood not just as a set of capabilities|such as the ability to monitor network traffic—but as a set of priorities constrained by resource limitations. My research addresses the twin themes of modeling and circumvention. With a grounding in empirical research, I build up an abstract model of the circumvention problem and examine how to adapt it to concrete censorship challenges. I describe the results of experiments on censors that probe their strengths and weaknesses; specifically, on the subject of active probing to discover proxy servers, and on delays in their reaction to changes in circumvention. I present two circumvention designs: domain fronting, which derives its resistance to blocking from the censor's reluctance to block other useful services; and Snowflake, based on quickly changing peer-to-peer proxy servers. I hope to change the perception that the circumvention problem is a cat-and-mouse game that affords only incremental and temporary advancements. -
Array AG 9.4 CLI Handbook
Array AG 9.4 CLI Handbook Copyright Statement Copyright Statement Copyright©2000-2018 Array Networks, Inc., 1371 McCarthy Blvd, Milpitas, California 95035, USA. All rights reserved. This document is protected by copyright and distributed under licenses restricting its use, copying, distribution, and compilation. No part of this document can be reproduced in any form by any means without prior written authorization of Array Networks. Documentation is provided “as is” without warranty of any kind, either express or implied, including any kind of implied or express warranty of non-infringement or the implied warranties of merchantability or fitness for a particular purpose. Array Networks reserves the right to change any products described herein at any time, and without notice. Array Networks assumes no responsibility or liability arising from the use of products described herein, except as expressly agreed to in writing by Array Networks. The use and purchase of this product does not convey a license to any patent copyright, or trademark rights, or any other intellectual property rights of Array Networks. Warning: Modifications made to the Array Networks unit, unless expressly approved by Array Networks, could void the user’s authority to operate the equipment. Declaration of Conformity We, Array Networks, Inc., 1371 McCarthy Blvd, Milpitas, CA 95035, 1-866-692-7729; declare under our sole responsibility that the product(s) Array Networks, Array Appliance complies with Part 15 of FCC Rules. Operation is subject to the following two conditions: (1) this device can not cause harmful interference, and (2) this device must accept any interference received, including interference that can cause undesired operation. -
Enhancing System Transparency, Trust, and Privacy with Internet Measurement
Enhancing System Transparency, Trust, and Privacy with Internet Measurement by Benjamin VanderSloot A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Computer Science and Engineering) in the University of Michigan 2020 Doctoral Committee: Professor J. Alex Halderman, Chair Assistant Professor Roya Ensafi Research Professor Peter Honeyman Assistant Professor Baris Kasikci Professor Kentaro Toyama Benjamin VanderSloot [email protected] ORCID iD: 0000-0001-6528-3927 © Benjamin VanderSloot 2020 ACKNOWLEDGEMENTS First and foremost, I thank my wife-to-be, Alexandra. Without her unwavering love and support, this dissertation would have remained unfinished. Without her help, the ideas here would not be as strong. Without her, I would not be here. Thanks are also due to my advisor, J. Alex Halderman, for giving me the independence and support I needed to find myself. I also thank Peter Honeyman for sharing his experience freely, both with history lessons and mentorship. Thank you Roya Ensafi, for watching out for me since we met. Thank you Baris Kasikci and Kentaro Toyama, for helping me out the door, in spite of the ongoing pandemic. I owe a great debt to my parents, Craig and Teresa VanderSloot, for raising me so well. No doubt the lessons about perseverance and hard work were put to good use. Your pride has been fuel to my fire for a very long time now. I also owe so much to my sister, Christine Kirbitz, for being the best example a little brother could hope for. I always had a great path to follow and an ear to share my problems with. -
A Privacy Threat for Internet Users in Internet-Censoring Countries
A Privacy Threat for Internet Users in Internet-censoring Countries Feno Heriniaina R. College of Computer Science, Chongqing University, Chongqing, China Keywords: Censorship, Human Computer Interaction, Privacy, Virtual Private Networks. Abstract: Online surveillance has been increasingly used by different governments to control the spread of information on the Internet. The magnitude of this activity differs widely and is based primarily on the areas that are deemed, by the state, to be critical. Aside from the use of keywords and the complete domain name filtering technologies, Internet censorship can sometimes even use the total blocking of IP addresses to censor content. Despite the advances, in terms of technology used for Internet censorship, there are also different types of circumvention tools that are available to the general public. In this paper, we report the results of our investigation on how migrants who previously had access to the open Internet behave toward Internet censorship when subjected to it. Four hundred and thirty-two (432) international students took part in the study that lasted two years. We identified the most common circumvention tools that are utilized by the foreign students in China. We investigated the usability of these tools and monitored the way in which they are used. We identified a behaviour-based privacy threat that puts the users of circumvention tools at risk while they live in an Internet-censoring country. We also recommend the use of a user-oriented filtering method, which should be considered as part of the censoring system, as it enhances the performance of the screening process and recognizes the real needs of its users. -
Internet Censorship in Thailand: User Practices and Potential Threats
Internet Censorship in Thailand: User Practices and Potential Threats Genevieve Gebhart∗†1, Anonymous Author 2, Tadayoshi Kohno† ∗Electronic Frontier Foundation †University of Washington [email protected] [email protected] 1 Abstract—The “cat-and-mouse” game of Internet censorship security community has proposed novel circumvention and circumvention cannot be won by capable technology methods in response [10, 25, 38]. alone. Instead, that technology must be available, The goal of circumventing censorship and attaining freer comprehensible, and trustworthy to users. However, the field access to information, however, relies on those largely focuses only on censors and the technical means to circumvent them. Thailand, with its superlatives in Internet circumvention methods being available, comprehensible, use and government information controls, offers a rich case and trustworthy to users. Only by meeting users’ needs can study for exploring users’ assessments of and interactions with circumvention tools realize their full technical capabilities. censorship. We survey 229 and interview 13 Internet users in With this goal in mind, the field lacks sufficient inquiry Thailand, and report on their current practices, experienced into the range of user perceptions of and interactions with and perceived threats, and unresolved problems regarding censorship. How do users assess censored content? What is censorship and digital security. Our findings indicate that the range of their reactions when they encounter existing circumvention tools were adequate for respondents to censorship? How does censorship affect the way they not access blocked information; that respondents relied to some only access but also produce information? extent on risky tool selection and inaccurate assessment of blocked content; and that attempts to take action with In addition to guiding more thorough anti-circumvention sensitive content on social media led to the most concrete strategies, these questions about users and censorship can threats with the least available technical defenses. -
Predictroute: a Network Path Prediction Toolkit
PredictRoute: A Network Path Prediction Toolkit RACHEE SINGH, University of Massachusetts, Amherst, USA DAVID TENCH, University of Massachusetts, Amherst, USA PHILLIPA GILL, University of Massachusetts, Amherst, USA ANDREW MCGREGOR, University of Massachusetts, Amherst, USA Accurate prediction of network paths between arbitrary hosts on the Internet is of vital importance for network operators, cloud providers, and academic researchers. We present PredictRoute, a system that predicts network paths between hosts on the Internet using historical knowledge of the data and control plane. In addition to feeding on freely available traceroutes and BGP routing tables, PredictRoute optimally explores network paths towards chosen BGP prefixes. PredictRoute’s strategy for exploring network paths discovers 4X more autonomous system (AS) hops than other well-known strategies used in practice today. Using a corpus of traceroutes, PredictRoute trains probabilistic models of routing towards prefixes on the Internet to predict network paths and their likelihood. PredictRoute’s AS-path predictions differ from the measured path byat most 1 hop, 75% of the time. We expose PredictRoute’s path prediction capability via a REST API to facilitate its inclusion in other applications and studies. We additionally demonstrate the utility of PredictRoute in improving real-world applications for circumventing Internet censorship and preserving anonymity online. CCS Concepts: • Mathematics of computing ! Paths and connectivity problems; Markov networks; • Net- works ! Routing protocols; Wide area networks; Public Internet. Additional Key Words and Phrases: network measurement; Internet path prediction ACM Reference Format: Rachee Singh, David Tench, Phillipa Gill, and Andrew McGregor. 2021. PredictRoute: A Network Path Prediction Toolkit . Proc. ACM Meas. Anal. Comput. Syst. -
The Use of TLS in Censorship Circumvention
The use of TLS in Censorship Circumvention Sergey Frolov Eric Wustrow University of Colorado Boulder University of Colorado Boulder [email protected] [email protected] Abstract—TLS, the Transport Layer Security protocol, has TLS [54], and adoption continues to grow as more websites, quickly become the most popular protocol on the Internet, already services, and applications switch to TLS. used to load over 70% of web pages in Mozilla Firefox. Due to its ubiquity, TLS is also a popular protocol for censorship Given the prevalence of TLS, it is commonly used by circumvention tools, including Tor and Signal, among others. circumvention tools to evade Internet censorship. Because However, the wide range of features supported in TLS makes censors can easily identify and block custom protocols [30], it possible to distinguish implementations from one another by circumvention tools have turned to using existing protocols. what set of cipher suites, elliptic curves, signature algorithms, and TLS offers a convenient choice for these tools, providing other extensions they support. Already, censors have used deep plenty of legitimate cover traffic from web browsers and packet inspection (DPI) to identify and block popular circumven- other TLS user, protection of content from eavesdroppers, and tion tools based on the fingerprint of their TLS implementation. several libraries to choose from that support it. In response, many circumvention tools have attempted to mimic popular TLS implementations such as browsers, but this However, simply using TLS for a transport protocol is technique has several challenges. First, it is burdensome to keep not enough to evade censors. Since TLS handshakes are not up with the rapidly-changing browser TLS implementations, and encrypted, censors can identify a client’s purported support for know what fingerprints would be good candidates to mimic. -
The Tor Project
The Tor Project Our mission is to be the global resource for technology, advocacy, research and education in the ongoing pursuit of freedom of speech, privacy rights online, and censorship circumvention. 1 ● Online Anonymity – Open Source – Open Network ● Community of researchers, developers, users and relay operators. ● U.S. 50 !c)!#" non$ profit or&anization 2 Estimated 2,000,000 to 8,000,000 daily Tor users 3 Threat model: what can the attacker do? Alice Anonymity network Bob watch Alice! watch (or be!) Bob! Control part of the network! 4 Anonymity isn't encryption: Encryption just protects contents. “Hi, Bob!” “Hi, Bob!” Alice <gibberish> attacker Bob 5 6 Anonymity serves different interests for different user groups. Anonymity “It's privacy!” Private citizens 7 Anonymity serves different interests for different user groups. Anonymity Businesses “It's network security!” “It's privacy!” Private citizens 8 Anonymity serves different interests for different user groups. “It's traffic-analysis resistance!” Governments Anonymity Businesses “It's network security!” “It's privacy!” Private citizens 9 Anonymity serves different interests for different user groups. Human rights “It's reachability!” “It's traffic-analysis activists resistance!” Governments Anonymity Businesses “It's network security!” “It's privacy!” Private citizens 10 The simplest designs use a single relay to hide connections. Alice1 Bob1 E(B ob3 ” ,“X “Y ”) Relay Alice2 E(Bob1, “Y”) “Z” Bob2 ”) “X , “Z ” ob2 Alice3 E(B Bob3 (example: some commercial proxy providers) 11 But a central relay is a single point of failure. Alice1 Bob1 E(B ob3 ” ,“X “Y ”) Evil Alice2 E(Bob1, “Y”) Relay “Z” Bob2 ”) “X , “Z ” ob2 Alice3 E(B Bob3 12 .. -
Marionette: a Programmable Network Traffic Obfuscation System Kevin P
Marionette: A Programmable Network Traffic Obfuscation System Kevin P. Dyer, Portland State University; Scott E. Coull, RedJack LLC.; Thomas Shrimpton, Portland State University https://www.usenix.org/conference/usenixsecurity15/technical-sessions/presentation/dyer This paper is included in the Proceedings of the 24th USENIX Security Symposium August 12–14, 2015 • Washington, D.C. ISBN 978-1-939133-11-3 Open access to the Proceedings of the 24th USENIX Security Symposium is sponsored by USENIX Marionette: A Programmable Network-Traffic Obfuscation System Kevin P. Dyer Scott E. Coull Thomas Shrimpton Portland State University RedJack, LLC. Portland State University [email protected] [email protected] [email protected] Abstract recently, the application layer. The latter looks for spe- cific features of packet payloads that act as a signature Recently, a number of obfuscation systems have been for the application-layer protocol being transported. developed to aid in censorship circumvention scenarios where encrypted network traffic is filtered. In this pa- To combat application-layer filtering, several sys- per, we present Marionette, the first programmable net- tems have been proposed to obfuscate packet payloads, work traffic obfuscation system capable of simultane- and generally hide the true protocol being transported. ously controlling encrypted traffic features at a variety Broadly speaking, these methods fall into one of three of levels, including ciphertext formats, stateful protocol categories: those that use encryption to fully random- -
Conjure: Summoning Proxies from Unused Address Space
Conjure: Summoning Proxies from Unused Address Space Sergey Frolov Jack Wampler Sze Chuen Tan University of Colorado Boulder University of Colorado Boulder UIUC J. Alex Halderman Nikita Borisov Eric Wustrow University of Michigan UIUC University of Colorado Boulder ABSTRACT Refraction Networking (formerly known as “Decoy Routing”) has emerged as a promising next-generation approach for circumvent- ing Internet censorship. Rather than trying to hide individual cir- cumvention proxy servers from censors, proxy functionality is implemented in the core of the network, at cooperating ISPs in friendly countries. Any connection that traverses these ISPs could be a conduit for the free flow of information, so censors cannot eas- ily block access without also blocking many legitimate sites. While one Refraction scheme, TapDance, has recently been deployed at ISP-scale, it suffers from several problems: a limited number of “decoy” sites in realistic deployments, high technical complexity, Figure 1: Conjure Overview — An ISP deploys a Conjure station, which and undesirable tradeoffs between performance and observability sees a passive tap of passing traffic. Following a steganographic registration by the censor. These challenges may impede broader deployment process, a client can connect to an unused IP address in the ISP’s AS, and and ultimately allow censors to block such techniques. the station will inject packets to communicate with the client as if there were a proxy server at that address. We present Conjure, an improved Refraction Networking ap- proach that overcomes these limitations by leveraging unused ad- dress space at deploying ISPs. Instead of using real websites as the decoy destinations for proxy connections, our scheme connects 1 INTRODUCTION to IP addresses where no web server exists leveraging proxy func- Over half of Internet users globally now live in countries that block tionality from the core of the network. -
Protocol Proxy: an FTE-Based Covert Channel
Computers & Security 92 (2020) 101777 Contents lists available at ScienceDirect Computers & Security journal homepage: www.elsevier.com/locate/cose Protocol Proxy: An FTE-based covert channel ∗ Jonathan Oakley , Lu Yu, Xingsi Zhong, Ganesh Kumar Venayagamoorthy, Richard Brooks Department of Electrical and Computer Engineering, Clemson University, Clemson, SC, USA a r t i c l e i n f o a b s t r a c t Article history: In a hostile network environment, users must communicate without being detected. This involves blend- Received 25 September 2019 ing in with the existing traffic. In some cases, a higher degree of secrecy is required. We present a proof- Revised 24 December 2019 of-concept format transforming encryption (FTE)-based covert channel for tunneling TCP traffic through Accepted 22 February 2020 protected static protocols. Protected static protocols are UDP-based protocols with variable fields that can- Available online 24 February 2020 not be blocked without collateral damage, such as power grid failures. We (1) convert TCP traffic to UDP Keywords: traffic, (2) introduce observation-based FTE, and (3) model interpacket timing with a deterministic Hid- Covert channel den Markov Model (HMM). The resulting Protocol Proxy has a very low probability of detection and is Format Transforming Encryption (FTE) an alternative to current covert channels. We tunnel a TCP session through a UDP protocol and guaran- Steganography tee delivery. Observation-based FTE ensures traffic cannot be detected by traditional rule-based analysis Traffic analysis or DPI. A deterministic HMM ensures the Protocol Proxy accurately models interpacket timing to avoid Deep Packet Inspection (DPI) detection by side-channel analysis.