The Internet's size and complexity make it difficult to understand what happens to network packets as they travel from source to destination. Internet service providers and governments sometimes interfere with users' online activities, further complicating this task. This project advances the scientific understanding of network interference detection by developing new methods to remotely measure the manipulation of Internet traffic, such as attempts to censor, tamper with, and monitor users' online activities. The newly proposed techniques can achieve an unprecedented level of detail about network manipulation around the world. Network interference and censorship harms U.S. economic interests, national security, and the human rights of citizens in censored countries. By working towards a better scientific understanding of the techniques used for detecting and monitoring such interference, this project can defend Internet users from unwarranted network manipulation. Past research has used resources such as PlanetLab, Virtual Private Networks (VPNs), and end-user machines to measure network disruptions. These vantage points scale poorly and have limited geographical coverage. They are difficult to deploy in practice and are unable to continuously collect data. In contrast, systems such as Spooky, Augur, and Iris (developed in the principal investigator's preliminary work) allow measurement systems to infer whether a remote system has network connectivity to another remote system without needing control of either. To do this, these systems exploit features in existing Internet protocols and infrastructure to interact with remote systems, and learn from their responses whether or not they were able to interact with other targeted hosts. These techniques overcome the problems of vantage point location and of recruiting participants