Measuring Censorship in Iran Using Refraction-based Proxies

Refraction networking deploys circumvention proxies inside cooperating ISPs that intercept TLS flows in transit, giving censored users a proxy whose externally observable destination is an arbitrary uncensored "decoy" host rather than a known proxy IP. The authors use refraction-based proxies as a measurement vantage point inside Iran to characterise the country's evolving censorship apparatus, including SNI-based filtering, protocol-fingerprinting, and adaptive responses to popular circumvention tools. The paper documents how Iranian filtering changes over time, identifies which destinations and protocols are blocked, and discusses implications for the design of robust circumvention systems facing a heterogeneous censor.