Practical Countermeasures Against Network Censorship
Practical Countermeasures against Network Censorship by Sergey Frolov B.S.I.T., Lobachevsky State University, 2015 M.S.C.S., University of Colorado, 2017 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Computer Science 2020 Committee Members: Eric Wustrow, Chair Prof. Sangtae Ha Prof. Nolen Scaife Prof. John Black Prof. Eric Keller Dr. David Fifield ii Frolov, Sergey (Ph.D., Computer Science) Practical Countermeasures against Network Censorship Thesis directed by Prof. Eric Wustrow Governments around the world threaten free communication on the Internet by building increasingly complex systems to carry out Network Censorship. Network Censorship undermines citizens’ ability to access websites and services of their preference, damages freedom of the press and self-expression, and threatens public safety, motivating the development of censorship circumvention tools. Inevitably, censors respond by detecting and blocking those tools, using a wide range of techniques including Enumeration Attacks, Deep Packet Inspection, Traffic Fingerprinting, and Active Probing. In this dissertation, I study some of the most common attacks, actually adopted by censors in practice, and propose novel attacks to assist in the development of defenses against them. I describe practical countermeasures against those attacks, which often rely on empiric measurements of real-world data to maximize their efficiency. This dissertation also reports how this work has been successfully deployed to several popular censorship circumvention tools to help censored Internet users break free of the repressive information control. iii Acknowledgements I am thankful to many engineers and researchers from various organizations I had a pleasure to work with, including Google, Tor Project, Psiphon, Lantern, and several universities.
[Show full text]