PrivacyMeter: Designing and developing a privacy-preserving browser extension

Anti-tracking browser extensions are popular among web users since they provide them with the ability to limit the number of trackers who get to learn about their browsing habits. These extensions however are limited in that they ignore other privacy signals, such as, the presence of a privacy policy, use of HTTPS, or presence of insecure web forms that can leak PII. To effectively inform users about the privacy consequences of visiting particular websites, we design, implement, and evaluate PrivacyMeter, a browser extension that, on-the-fly, computes a relative privacy score for any website that a user is visiting. This score is computed based on each website’s privacy practices and how these compare to the privacy practices of other pre-analyzed websites. We report on the development of PrivacyMeter with respect to the requirements for coverage of privacy practices, accuracy of measurement, and low performance overhead. We show how relative privacy scores help in interpreting results as different categories of websites have different standards across the monitored privacy parameters. Finally, we discuss the power of crowdsourcing for privacy research, and the existing challenges of properly incorporating crowdsourcing in a way that protects user anonymity while allowing the service to defend against malicious clients.