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Stanford University Networking Seminar


Roya Ensafi (Princeton University)
Studying the Great Firewall of China: From Internet Filtering to Actively Probing Anti-Censorship Tools

12:15pm, Thursday, April 28 2016
Gates 104

About the Talk

Almost 20 years ago, the Chinese government initiated legislation to regulate the Internet in Mainland China, resulting in the birth of a national firewall known as the Great Firewall of China (GFW). The GFW’s main goal is to monitor incoming and outgoing traffic and disrupt prohibited connections. In the past couple of years, the operational development of the GFW has significantly escalated state-level information control. To enforce the censorship policies, the GFW developed and implemented sophisticated techniques to actively attack anti-censorship tools. In this talk, I will give a detailed overview of a decade-long arms race between Tor and the GFW. Then, I will paint a detailed picture of the GFW’s active probing system that is deployed to detect and block hidden circumvention tools. I will show that the system makes use of a large amount of IP addresses, provide evidence that all these IP addresses are centrally controlled, and determine the location of the Great Firewall’s sensors.

About the Speaker

Roya Ensafi is a Postdoctoral Research Associate and a fellow at the Center for Information Technology Policy (CITP) at Princeton University. Her research work focuses on computer networking and security, with an emphasis on network measurement. The primary goal of her current research is to better understand and bring transparency to network interference (e.g. censorship) by designing new tools and techniques. In her dissertation, which passed with distinction, Roya developed side channels to remotely measure TCP connectivity between two hosts, without requiring access to any of the hosts. Most of her latest research projects center around studying national firewalls, especially the Great Firewall of China (GFW). Her work studying how the Great Firewall of China discovers hidden circumvention servers received an IRTF Applied Networking Research Prize (ANRP) in 2016. Her work has been published in the USENIX Security Symposium, the ACM Internet Measurement Conference, and the Symposium on Privacy Enhancing Technologies. While a Ph.D. student at the University of New Mexico, she received the Sigma Xi Research Excellence and the UNM Best Graduate Student Mentor awards.