CDNBrowsing is a promising approach recently proposed for censorship circumvention. CDNBrowsing relies on the fact that blocking content hosted on public CDNs can potentially cause the censors collateral damage due to disrupting benign content publishers. In this work, we identify various low-cost attacks against CDNBrowsing, demonstrating that the design of practically unobservable CDNBrowsing systems is significantly more challenging than what thought previously. We particularly devise unique website fingerprinting attacks against CDNBrowsing traffic, and discover various forms of information leakage in HTTPS that can be used to block the previously proposed CDNBrowsing system. Motivated by the attacks, we design and implement a new CDNBrowsing system called CDNReaper, which defeats the discovered attacks. By design, a CDNBrowsing system can browse only particular types of webpages due to its proxy-less design. We perform a comprehensive measurement to classify popular Internet websites based on their browsability by CDNBrowsing systems. To further increase the reach of CDNBrowsing, we devise several mechanisms that enable CDNBrowsing systems to browse a larger extent of Internet webpages, particularly partial-CDN webpages.

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repressive regimes additionally utilize advanced networking tools, including deep packet inspection (DPI), to prevent the use of the censorship circumvention technologies by their citizens [81], [16], [36], [37]. We have built and deployed MassBrowser as a fully operational system with end-user GUI software for major operating systems. Our system has been in the beta release mode for over a year with hundreds of invited users from major censored countries testing it on a daily basis.