Peter J. Snyder

Alex Davidson, Peter Snyder, E. B. Quirk et al.

Threshold aggregation reporting systems promise a practical, privacy-preserving solution for developers to learn how their applications are used "\emph{in-the-wild}". Unfortunately, proposed systems to date prove impractical for wide scale adoption, suffering from a combination of requiring: \emph{i)} prohibitive trust assumptions; \emph{ii)} high computation costs; or \emph{iii)} massive user bases. As a result, adoption of truly-private approaches has been limited to only a small number of enormous (and enormously costly) projects. In this work, we improve the state of private data collection by proposing $\mathsf{STAR}$, a highly efficient, easily deployable system for providing cryptographically-enforced $κ$-anonymity protections on user data collection. The $\mathsf{STAR}$ protocol is easy to implement and cheap to run, all while providing privacy properties similar to, or exceeding the current state-of-the-art. Measurements of our open-source implementation of $\mathsf{STAR}$ find that it is $1773\times$ quicker, requires $62.4\times$ less communication, and is $24\times$ cheaper to run than the existing state-of-the-art.

Jordan Jueckstock, Peter Snyder, Shaown Sarker et al.

While much current web privacy research focuses on browser fingerprinting, the boring fact is that the majority of current third-party web tracking is conducted using traditional, persistent-state identifiers. One possible explanation for the privacy community's focus on fingerprinting is that to date browsers have faced a lose-lose dilemma when dealing with third-party stateful identifiers: block state in third-party frames and break a significant number of webpages, or allow state in third-party frames and enable pervasive tracking. The alternative, middle-ground solutions that have been deployed all trade privacy for compatibility, rely on manually curated lists, or depend on the user to manage state and state-access themselves. This work furthers privacy on the web by presenting a novel system for managing the lifetime of third-party storage, "page-length storage". We compare page-length storage to existing approaches for managing third-party state and find that page-length storage has the privacy protections of the most restrictive current option (i.e., blocking third-party storage) but web-compatibility properties mostly similar to the least restrictive option (i.e., allowing all third-party storage). This work further compares page-length storage to an alternative third-party storage partitioning scheme and finds that page-length storage provides superior privacy protections with comparable web-compatibility. We provide a dataset of the privacy and compatibility behaviors observed when applying the compared third-party storage strategies on a crawl of the Tranco 1k and the quantitative metrics used to demonstrate that page-length storage matches or surpasses existing approaches. Finally, we provide an open-source implementation of our page-length storage approach, implemented as patches against Chromium.

Philipp Winter, Anna Harbluk Lorimer, Peter Snyder et al.

Much of the recent excitement around decentralized finance (DeFi) comes from hopes that DeFi can be a secure, private, less centralized alternative to traditional finance systems. However, people moving to DeFi sites in hopes of improving their security and privacy may end up with less of both as recent attacks have demonstrated. In this work, we improve the understanding of DeFi by conducting the first Web measurements of the security, privacy, and decentralization properties of popular DeFi front ends. We find that DeFi applications -- or dapps -- suffer from the same security and privacy risks that frequent other parts of the Web but those risks are greatly exacerbated considering the money that is involved in DeFi. Our results show that a common tracker can observe user behavior on over 56% of websites we analyzed and many trackers on DeFi sites can trivially link a user's Ethereum address with PII (e.g., user name or demographic information), or phish users by initiating fake Ethereum transactions. Lastly, we establish that despite claims to the opposite, because of companies like Amazon and Cloudflare operating significant Web infrastructure, DeFi as a whole is considerably less decentralized than previously believed.

Panagiotis Papadopoulos, Peter Snyder, Dimitrios Athanasakis et al.

Funding the production of quality online content is a pressing problem for content producers. The most common funding method, online advertising, is rife with well-known performance and privacy harms, and an intractable subject-agent conflict: many users do not want to see advertisements, depriving the site of needed funding. Because of these negative aspects of advertisement-based funding, paywalls are an increasingly popular alternative for websites. This shift to a "pay-for-access" web is one that has potentially huge implications for the web and society. Instead of a system where information (nominally) flows freely, paywalls create a web where high quality information is available to fewer and fewer people, leaving the rest of the web users with less information, that might be also less accurate and of lower quality. Despite the potential significance of a move from an "advertising-but-open" web to a "paywalled" web, we find this issue understudied. This work addresses this gap in our understanding by measuring how widely paywalls have been adopted, what kinds of sites use paywalls, and the distribution of policies enforced by paywalls. A partial list of our findings include that (i) paywall use is accelerating (2x more paywalls every 6 months), (ii) paywall adoption differs by country (e.g. 18.75% in US, 12.69% in Australia), (iii) paywalls change how users interact with sites (e.g. higher bounce rates, less incoming links), (iv) the median cost of an annual paywall access is $108 per site, and (v) paywalls are in general trivial to circumvent. Finally, we present the design of a novel, automated system for detecting whether a site uses a paywall, through the combination of runtime browser instrumentation and repeated programmatic interactions with the site. We intend this classifier to augment future, longitudinal measurements of paywall use and behavior.

Peter Snyder, Antoine Vastel, Benjamin Livshits

Ad and tracking blocking extensions are popular tools for improving web performance, privacy and aesthetics. Content blocking extensions typically rely on filter lists to decide whether a web request is associated with tracking or advertising, and so should be blocked. Millions of web users rely on filter lists to protect their privacy and improve their browsing experience. Despite their importance, the growth and health of filter lists are poorly understood. Filter lists are maintained by a small number of contributors, who use a variety of undocumented heuristics to determine what rules should be included. Lists quickly accumulate rules, and rules are rarely removed. As a result, users' browsing experiences are degraded as the number of stale, dead or otherwise not useful rules increasingly dwarf the number of useful rules, with no attenuating benefit. An accumulation of "dead weight" rules also makes it difficult to apply filter lists on resource-limited mobile devices. This paper improves the understanding of crowdsourced filter lists by studying EasyList, the most popular filter list. We find that EasyList has grown from several hundred rules, to well over 60,000 rules, during its 9-year history. We measure how EasyList affects web browsing by applying EasyList to a sample of 10,000 websites. We find that 90.16% of the resource blocking rules in EasyList provide no benefit to users in common browsing scenarios. We further use our changes in EasyList application rates to provide a taxonomy of the ways advertisers evade EasyList rules. Finally, we propose optimizations for popular ad-blocking tools, that allow EasyList to be applied on performance constrained mobile devices, and improve desktop performance by 62.5%, while preserving over 99% of blocking coverage.