NSF Award
2323193
Billions of people worldwide live in regions that perform automated censorship of Internet traffic and other forms of traffic tampering. Understanding how users are affected by such censorship is of critical importance in developing technologies and policies that promote more free and open access to information. Prior efforts to measure Internet censorship have focused on active measurements, which involve procuring vantage points and then issuing queries from a test-list of domain names or keywords to determine what is being censored where. While these efforts have proven invaluable, relying on active measurements alone imposes several limitations, chief among them being that they can only measure what could be censored, not what users are actively experiencing. This project's novelties are a collection of measurement tools that passively detect censorship as it occurs with real users' Internet traffic. The project's broader significance and importance are that it allows datasets to be collected that are not possible with active measurements alone; the proposed project's passive techniques can rapidly detect newly censored content, and they capture what users are actively experiencing.<br/><br/>The central insight behind the project is that censorship can be detected through "tamper signatures": tell-tale signs of traffic tampering by a third party, such as suspiciously timed connection tear-down packets or duplicate responses to unencrypted queries. The project is organized along different deployment scenarios that each raise unique technical challenges when detecting tamper signatures: a customized measurement tool for server-side deployments, one for client-side deployments, and one for in-network deployments (such as at an Internet Service Provider). This collection of measurement tools is expected to permit censorship measurements at many disparate vantage points around the world. The project is thus also developing techniques that will allow multiple networks to share their data safely and responsibly.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
