Visible to the public Biblio

Filters: Author is Christin, Nicolas  [Clear All Filters]
Colnago, Jessica, Devlin, Summer, Oates, Maggie, Swoopes, Chelse, Bauer, Lujo, Cranor, Lorrie, Christin, Nicolas.  2018.  "It's Not Actually That Horrible'': Exploring Adoption of Two-Factor Authentication at a University. Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems. :456:1-456:11.

Despite the additional protection it affords, two-factor authentication (2FA) adoption reportedly remains low. To better understand 2FA adoption and its barriers, we observed the deployment of a 2FA system at Carnegie Mellon University (CMU). We explore user behaviors and opinions around adoption, surrounding a mandatory adoption deadline. Our results show that (a) 2FA adopters found it annoying, but fairly easy to use, and believed it made their accounts more secure; (b) experience with CMU Duo often led to positive perceptions, sometimes translating into 2FA adoption for other accounts; and, (c) the differences between users required to adopt 2FA and those who adopted voluntarily are smaller than expected. We also explore the relationship between different usage patterns and perceived usability, and identify user misconceptions, insecure practices, and design issues. We conclude with recommendations for large-scale 2FA deployments to maximize adoption, focusing on implementation design, use of adoption mandates, and strategic messaging.

Sharif, Mahmood, Urakawa, Jumpei, Christin, Nicolas, Kubota, Ayumu, Yamada, Akira.  2018.  Predicting Impending Exposure to Malicious Content from User Behavior. Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security. :1487–1501.
Many computer-security defenses are reactive—they operate only when security incidents take place, or immediately thereafter. Recent efforts have attempted to predict security incidents before they occur, to enable defenders to proactively protect their devices and networks. These efforts have primarily focused on long-term predictions. We propose a system that enables proactive defenses at the level of a single browsing session. By observing user behavior, it can predict whether they will be exposed to malicious content on the web seconds before the moment of exposure, thus opening a window of opportunity for proactive defenses. We evaluate our system using three months' worth of HTTP traffic generated by 20,645 users of a large cellular provider in 2017 and show that it can be helpful, even when only very low false positive rates are acceptable, and despite the difficulty of making "on-the-fly” predictions. We also engage directly with the users through surveys asking them demographic and security-related questions, to evaluate the utility of self-reported data for predicting exposure to malicious content. We find that self-reported data can help forecast exposure risk over long periods of time. However, even on the long-term, self-reported data is not as crucial as behavioral measurements to accurately predict exposure.
Ur, Blase, Alfieri, Felicia, Aung, Maung, Bauer, Lujo, Christin, Nicolas, Colnago, Jessica, Cranor, Lorrie Faith, Dixon, Henry, Emami Naeini, Pardis, Habib, Hana et al..  2017.  Design and Evaluation of a Data-Driven Password Meter. Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems. :3775–3786.
Despite their ubiquity, many password meters provide inaccurate strength estimates. Furthermore, they do not explain to users what is wrong with their password or how to improve it. We describe the development and evaluation of a data-driven password meter that provides accurate strength measurement and actionable, detailed feedback to users. This meter combines neural networks and numerous carefully combined heuristics to score passwords and generate data-driven text feedback about the user's password. We describe the meter's iterative development and final design. We detail the security and usability impact of the meter's design dimensions, examined through a 4,509-participant online study. Under the more common password-composition policy we tested, we found that the data-driven meter with detailed feedback led users to create more secure, and no less memorable, passwords than a meter with only a bar as a strength indicator.
Sawaya, Yukiko, Sharif, Mahmood, Christin, Nicolas, Kubota, Ayumu, Nakarai, Akihiro, Yamada, Akira.  2017.  Self-Confidence Trumps Knowledge: A Cross-Cultural Study of Security Behavior. Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems. :2202–2214.
Computer security tools usually provide universal solutions without taking user characteristics (origin, income level, ...) into account. In this paper, we test the validity of using such universal security defenses, with a particular focus on culture. We apply the previously proposed Security Behavior Intentions Scale (SeBIS) to 3,500 participants from seven countries. We first translate the scale into seven languages while preserving its reliability and structure validity. We then build a regression model to study which factors affect participants' security behavior. We find that participants from different countries exhibit different behavior. For instance, participants from Asian countries, and especially Japan, tend to exhibit less secure behavior. Surprisingly to us, we also find that actual knowledge influences user behavior much less than user self-confidence in their computer security knowledge. Stated differently, what people think they know affects their security behavior more than what they do know.
Soska, Kyle, Gates, Chris, Roundy, Kevin A., Christin, Nicolas.  2017.  Automatic Application Identification from Billions of Files. Proceedings of the 23rd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining. :2021–2030.

Understanding how to group a set of binary files into the piece of software they belong to is highly desirable for software profiling, malware detection, or enterprise audits, among many other applications. Unfortunately, it is also extremely challenging: there is absolutely no uniformity in the ways different applications rely on different files, in how binaries are signed, or in the versioning schemes used across different pieces of software. In this paper, we show that, by combining information gleaned from a large number of endpoints (millions of computers), we can accomplish large-scale application identification automatically and reliably. Our approach relies on collecting metadata on billions of files every day, summarizing it into much smaller "sketches", and performing approximate k-nearest neighbor clustering on non-metric space representations derived from these sketches. We design and implement our proposed system using Apache Spark, show that it can process billions of files in a matter of hours, and thus could be used for daily processing. We further show our system manages to successfully identify which files belong to which application with very high precision, and adequate recall.

Mazurek, Michelle L., Komanduri, Saranga, Vidas, Timothy, Bauer, Lujo, Christin, Nicolas, Cranor, Lorrie Faith, Kelley, Patrick Gage, Shay, Richard, Ur, Blase.  2013.  Measuring Password Guessability for an Entire University. Proceedings of the 2013 ACM SIGSAC Conference on Computer &\#38; Communications Security. :173–186.
Despite considerable research on passwords, empirical studies of password strength have been limited by lack of access to plaintext passwords, small data sets, and password sets specifically collected for a research study or from low-value accounts. Properties of passwords used for high-value accounts thus remain poorly understood. We fill this gap by studying the single-sign-on passwords used by over 25,000 faculty, staff, and students at a research university with a complex password policy. Key aspects of our contributions rest on our (indirect) access to plaintext passwords. We describe our data collection methodology, particularly the many precautions we took to minimize risks to users. We then analyze how guessable the collected passwords would be during an offline attack by subjecting them to a state-of-the-art password cracking algorithm. We discover significant correlations between a number of demographic and behavioral factors and password strength. For example, we find that users associated with the computer science school make passwords more than 1.5 times as strong as those of users associated with the business school. while users associated with computer science make strong ones. In addition, we find that stronger passwords are correlated with a higher rate of errors entering them. We also compare the guessability and other characteristics of the passwords we analyzed to sets previously collected in controlled experiments or leaked from low-value accounts. We find more consistent similarities between the university passwords and passwords collected for research studies under similar composition policies than we do between the university passwords and subsets of passwords leaked from low-value accounts that happen to comply with the same policies.
Forget, Alain, Komanduri, Saranga, Acquisti, Alessandro, Christin, Nicolas, Cranor, Lorrie Faith, Telang, Rahul.  2014.  Building the Security Behavior Observatory: An Infrastructure for Long-term Monitoring of Client Machines. Proceedings of the 2014 Symposium and Bootcamp on the Science of Security. :24:1–24:2.

We present an architecture for the Security Behavior Observatory (SBO), a client-server infrastructure designed to collect a wide array of data on user and computer behavior from hundreds of participants over several years. The SBO infrastructure had to be carefully designed to fulfill several requirements. First, the SBO must scale with the desired length, breadth, and depth of data collection. Second, we must take extraordinary care to ensure the security of the collected data, which will inevitably include intimate participant behavioral data. Third, the SBO must serve our research interests, which will inevitably change as collected data is analyzed and interpreted. This short paper summarizes some of our design and implementation benefits and discusses a few hurdles and trade-offs to consider when designing such a data collection system.