The Project

Censored Planet is a system for continuously monitoring global Internet censorship. It uses novel measurement techniques that remotely detect instances of interference almost anywhere on the Internet without end-user participation. Compared to previous approaches—which relied on having volunteers in censored regions deploy special hardware or software—this results in significantly better coverage, lower costs, and reduced ethical risk. This system allows us to continuously monitor the deployment of network interference technologies, track policy changes in censoring nations, and better understand the targets of interference. Making opaque censorship practices more transparent at a global scale could help counter the proliferation of these growing restrictions to online freedom.

How It Works

With the increasing focus on network management and growing prevalence of commodity DPI technology, network interference practices---such as censorship, surveillance, content injection, traffic throttling, and net neutrality violations---are on the rise.

The problem CensoredPlanet attempts to solve: Characterizing policy of remote firewalls.
CensoredPlanet Measures from 'off-path', without cooperation of either clients or servers.
Network interference can happen at each layer of Internet communication. CensoredPlanet aims to track all layers above the physical layer.

Past research has focused on the potential of distributed networks, including PlanetLab, VPNs, and volunteer end-user machines, to directly and systematically measure disruption. These vantage points offer direct access to a swath of networks, and can conduct measurements tailored to deepen understanding. Unfortunately, they scale poorly and have trouble covering even half of the countries on earth. In practice, tailored deployments are extremely time and labor intensive, and individual vantage points frequently suffer from periods of disruption. These methods also raise ethical issues: the user responsible for a machine may be held accountable for actions of a researcher. To ensure safety, researchers have had to resort to quizzes and in-person warnings of assumed risk.

CensoredPlanet uses a fundamentally different method that allows for global-scale observation of Internet connectivity and disruption.

These projects, Augur, Satellite, and Quack, use network side channels to remotely detect network anomalies. Critically, these systems allow us to learn whether a remote system B has network connectivity to another remote system C, without needing control of B or C. To do this, these systems make use of features in existing Internet protocols and infrastructure to interact with remote systems, and learn from their responses if they were able to interact with other targeted hosts. These techniques overcome the traditional limitations of vantage point and participant selection. With tens of thousands of vantage points, they provide an unprecedented breadth of coverage.

Research Projects

The following projects are part of Censored Planet.

  • Augur

    Internet-Wide Measurement of Network Layer Censorship

    Augur is a system that utilizes TCP/IP side channels to measure reachability between two Internet locations without directly controlling a measurement vantage point at either location. It is a scalable, statistically robust methods to infer network-layer filtering, and capable of performing continuous monitoring of global censorship. It is currently deployed and runs Internet-wide disruption tests in nearly 180 countries against sites known to be frequently blocked.

  • Satellite

    Global Detection Of DNS-Layer Censorship

    Satellite measures global trends in website deployment and accessibility via the consistency of DNS records. Satellite watches DNS resolution through active measurements of DNS resolvers across the IPv4 address space. A data-set of the alexa top 10,000 domains is collected each week. Satellite is committed to openness, with all code and data made publicly available.

  • Quack

    Scalable Remote Measurement of Application-Layer Censorship

    Quack is a technique for detecting content-level censorship. Quack sacrifices idenitification of tightly controlled DPI behavior in exchange for broad measurements of keywords and protocol disruption.


Censored Planet is funded by:

The National Science Foundation

The University of Michigan