In this work, we take a step towards understanding and defending against spying browser extensions. These are extensions repurposed to capture online activities of a user and communicate the collected sensitive information to a third-party domain. We conduct an empirical study of such extensions on the Chrome Web Store. First, we present an in-depth analysis of the spying behavior of these extensions. We observe that these extensions steal a variety of sensitive user information, such as the complete browsing history (e.g., the sequence of web traversals), online social network (OSN) access tokens, IP address, and geolocation. Second, we investigate the potential for automatically detecting spying extensions by applying machine learning schemes. We show that using a Recurrent Neural Network (RNN), the sequence of browser API calls made by an extension can be a robust feature, outperforming hand-crafted features (used in prior work on malicious extensions) to detect spying extensions. Our RNN based detection scheme achieves a high precision (90.02%) and recall (93.31%) in detecting spying extensions.

Cloud computing has evolved to meet user demands, from arbitrary VMs offered by IaaS to the narrow application interfaces of PaaS. Unfortunately, there exists an intermediate point that is not well met by today's offerings: users who wish to run arbitrary, already available binaries (as opposed to rewriting their own application for a PaaS) yet expect their applications to be long-lived but mostly idle (as opposed to the always-on VM of IaaS). For example, end users who wish to run their own email or DNS server.

Critical to the security of any public key infrastructure (PKI) is the ability to revoke previously issued certificates. While the overall SSL ecosystem is well-studied, the frequency with which certificates are revoked and the circumstances under which clients (e.g., browsers) check whether certificates are revoked are still not well-understood.

Central to the secure operation of a public key infrastructure (PKI) is the ability to revoke certificates. While much of users' security rests on this process taking place quickly, in practice, revocation typically requires a human to decide to reissue a new certificate and revoke the old one. Thus, having a proper understanding of how often systems administrators reissue and revoke certificates is crucial to understanding the integrity of a PKI. Unfortunately, this is typically difficult to measure: while it is relatively easy to determine when a certificate is revoked, it is difficult to determine whether and when an administrator should have revoked.

Over the past two decades, the web has provided dramatic improvements in the ease of sharing content. Unfortunately, the costs of distributing this content are largely incurred by web site operators; popular web sites are required to make substantial monetary investments in serving infrastructure or cloud computing resources---or must pay other organizations (e.g., content distribution networks)---to help serve content. Previous approaches to offloading some of the distribution costs onto end users have relied on client-side software or web browser plug-ins, providing poor user incentives and dramatically limiting their scope in practice.

Today, the data exchanged over online social networks (OSNs) represents a significant fraction of Internet traffic. However, OSN content is different from more traditional web content, as it is more likely to be generated at the edge of the network, to be exchanged within a local geographic region, and to possess a more even popularity distribution with fewer popular objects. Unfortunately, most OSNs still use largely centralized approaches to distribute content (e.g., CDNs and web caches), resulting in lower performance due to the different workload. In this paper, we take a first step towards addressing this situation by proposing Web Cloud, a content distribution system for OSNs that works by repurposing client web browsers to help serve content to others. When a user browses content, Web Cloud tries to serve the request from one of that user's friends' browsers, instead of from the OSN directly. Unlike other systems, Web Cloud works with existing browsers and does not require any plug-ins, and therefore can be directly applied to today's OSNs. We demonstrate the practicality of Web Cloud with micro benchmarks, simulations of a Facebook deployment, a real-world deployment, and evaluations of a proof-of-concept iOS app.