This paper presents a concurrent-computing approach-high-performance memory snapshotting-to improving security-introspection of virtual machine guest memory. Efficient introspection improves security monitoring in existing hypervisor systems with real-time, consistent memory introspection capabilities. Efficient introspection has three requirements that each must be met to provide protection against evasive threats: native memory introspection performance, accpetable guest performance, and consistent introspection view of guest memory. Existing introspection systems have provided one or two of these properties but not all three at once. High-performance memory snapshots are evaluated as a solution for meeting all three efficient introspection requirements. In this work we describe how existing system performance can be improved with high-performance snapshotting, present an efficient introspection prototype that has been released as an element of the open-source LibVMI introspection library1, evaluate the efficient introspection prototype on both applications and microbenchmarks, provide demonstrations of introspection application modules enabled by efficient introspection, and provide performance guidance for developing introspection applications utilizing efficient introspection.

The programming education literature includes many observations that pass rates are low in introductory programming courses, but few or no comparisons of student performance across courses. This paper addresses that shortcoming. Having included a small set of identical questions in the final examinations of a number of introductory programming courses, we illustrate the use of these questions to examine the relative performance of the students both across multiple institutions and within some institutions. We also use the questions to quantify the size and overall difficulty of each exam. We find substantial differences across the courses, and venture some possible explanations of the differences. We conclude by explaining the potential benefits to instructors of using the same questions in their own exams.

Ten selected questions have been included in 13 introductory programming exams at seven institutions in five countries. The students' results on these questions, and on the exams as a whole, lead to the development of a benchmark against which the exams in other introductory programming courses can be assessed. We illustrate some potential benefits of comparing exam performance against this benchmark, and show other uses to which it can be put, for example to assess the size and the overall difficulty of an exam. We invite others to apply the benchmark to their own courses and to share the results with us.

Users often have rich and complex photo-sharing preferences, but properly configuring access control can be difficult and time-consuming. In an 18-participant laboratory study, we explore whether the keywords and captions with which users tag their photos can be used to help users more intuitively create and maintain access-control policies. We find that (a) tags created for organizational purposes can be repurposed to create efficient and reasonably accurate access-control rules; (b) users tagging with access control in mind develop coherent strategies that lead to significantly more accurate rules than those associated with organizational tags alone; and (c) participants can understand and actively engage with the concept of tag-based access control.

As users store and share more digital content at home, access control becomes increasingly important. One promising approach for helping non-expert users create accurate access policies is reactive policy creation, in which users can update their policy dynamically in response to access requests that would not otherwise succeed. An earlier study suggested reactive policy creation might be a good fit for file access control at home. To test this, we conducted an experience-sampling study in which participants used a simulated reactive access-control system for a week. Our results bolster the case for reactive policy creation as one mode by which home users specify access-control policy. We found both quantitative and qualitative evidence of dynamic, situational policies that are hard to implement using traditional models but that reactive policy creation can facilitate. While we found some clear disadvantages to the reactive model, they do not seem insurmountable.