Scalable Remote Measurement of Application-Layer Disruption


Quack is a novel technique for measuring keyword blocking at the application layer in a scalable, longitudinal, and safe way.

Quack uses echo servers to detect DPI blocking of traffic based on request headers. The advantage of using echo servers is that identifying responses that have been interfered with is trivial and arbitrary TCP based protocols (in addition to HTTP) can be tested. By making use of echo's sibling discard protocol, we are able to determine the directionality of interference.


All the data collected from the Observatory is publicly available, including metadata.


Quack was presented at the 2018 USENIX Security Symposium.

August 2018 USENIX Security Symposium

Quack: Scalable Remote Measurement of Application-Layer Censorship

Benjamin VanderSloot Allison McDonald J. Alex Halderman Will Scott Roya Ensafi


title={Quack: Scalable Remote Measurement of Application-Layer Censorship},
author={Ben VanderSloot and Allison McDonald and Will Scott and J. Alex Halderman and Roya Ensafi},
booktitle={USENIX Security Symposium},


Quack for Censored Planet is developed and maintained by Ram Sundara Raman, Nick Ceccio and Roya Ensafi.

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