Shubhra Kanti, Karmaker Santu, Vincent Bindschadler, ChengXiang Zhai, and Carl A. Gunter recently published a paper titled NRF: A Naive Re-identification Framework:
The promise of big data relies on the release and aggregation of data sets. When these data sets contain sensitive information about individuals, it has been scalable and convenient to protect the privacy of these individuals by de-identification. However, studies show that the combination of de-identified data sets with other data sets risks re-identification of some records. Some studies have shown how to measure this risk in specific contexts where certain types of public data sets (such as voter roles) are assumed to be available to attackers. To the extent that it can be accomplished, such analyses enable the threat of compromises to be balanced against the benefits of sharing data. For example, a study that might save lives by enabling medical research may be enabled in light of a sufficiently low probability of compromise from sharing de-identified data. In this paper, we introduce a general probabilistic re-identification framework that can be instantiated in specific contexts to estimate the probability of compromises based on explicit assumptions. We further propose a baseline of such assumptions that enable a first-cut estimate of risk for practical case studies. We refer to the framework with these assumptions as the Naive Re-identification Framework (NRF). As a case study, we show how we can apply NRF to analyze and quantify the risk of re-identification arising from releasing de-identified medical data in the context of publicly-available social media data. The results of this case study show that NRF can be used to obtain meaningful quantification of the re-identification risk, compare the risk of different social media, and assess risks of combinations of various demographic attributes and medical conditions that individuals may voluntarily disclose on social media.
ACM Workshop on Privacy in an Electronic Society (WPES ’18), Toronto, Canada, October 2018. DOI: 10.1145/3267323.3268948
Karan Ganju, Qi Wang, Wei Yang, Carl A. Gunter, and Nikita Borisov recently published a paper titled Property Inference Attacks on Fully Connected Neural Networks using Permutation Invariant Representations:
With the growing adoption of machine learning, sharing of learned models is becoming popular. However, in addition to the prediction properties the model producer aims to share, there is also a risk that the model consumer can infer other properties of the training data the model producer did not intend to share. In this paper, we focus on the inference of global properties of the training data, such as the environment in which the data was produced, or the fraction of the data that comes from a certain class, as applied to white-box Fully Connected Neural Networks (FCNNs). Because of their complexity and inscrutability, FCNNs have a particularly high risk of leaking unexpected information about their training sets; at the same time, this complexity makes extracting this information challenging. We develop techniques that reduce this complexity by noting that FCNNs are invariant under permutation of nodes in each layer. We develop our techniques using representations that capture this invariance and simplify the information extraction task. We evaluate our techniques on several synthetic and standard benchmark datasets and show that they are very effective at inferring various data properties. We also perform two case studies to demonstrate the impact of our attack. In the first case study we show that a classifier that recognizes smiling faces also leaks information about the relative attractiveness of the individuals in its training set. In the second case study we show that a classifier that recognizes Bitcoin mining from performance counters also leaks information about whether the classifier was trained on logs from machines that were patched for the Meltdown and Spectre attacks.
ACM Computer and Communications Security (CCS ’18), Toronto Canada, October 2018. DOI:10.1145/3243734.3243834
Juhee Kwon and Eric Johnson recently published an article aimed at the question Does “meaningful-use” attestation improve information security performance?
Certification mechanisms are often employed to assess and signal difficult-to-observe management practices and foster improvement. In the U.S. healthcare sector, a certification mechanism called meaningful-use attestation was recently adopted as part of an effort to encourage electronic health record (EHR) adoption while also focusing healthcare providers on protecting sensitive healthcare data. This new regime motivated us to examine how meaningful-use attestation influences the occurrence of data breaches. Using a propensity score matching technique combined with a difference-in-differences (DID) approach, our study shows that the impact of meaningful-use attestation is contingent on the nature of data breaches and the time frame. Hospitals that attest to having reached Stage 1 meaningful-use standards observe fewer external breaches in the short term, but do not see continued improvement in the following year. On the other hand, attesting hospitals observe short-term increases in accidental internal breaches but eventually see long-term reductions. We do not find any link between malicious internal breaches and attestation. Our findings offer theoretical and practical insights into the effective design of certification mechanisms.
The full paper appears in in MIS Quarterly. Vol. 42, No. 4 (December), 1043-1067, 2018. DOI: 10.25300/MISQ/2018/13580
THaW’s A.J. Burns and Eric Johnson recently published a piece in IT Professional:
Issue No. 03 – May./Jun. (2018 vol. 20)
Scott Breece, VP and CISO of Community Health Systems, discusses the rising security threat in healthcare with M. Eric Johnson, Dean of Vanderbilt University’s Owen Graduate School of Management. Scott highlights how health IT is transforming healthcare, improving the patient experience and outcomes. However, digitization of healthcare data also creates new risks for the healthcare system. Scott discusses how Community Health Systems is staying ahead of those threats and securing patient data. This video was partially supported by the THaW project, which is co-led by Eric Johnson.
Tim Pierson’s dissertation work resulted in an innovative method for single-antenna Wi-Fi devices (like many mHealth devices, medical devices, or those in the IoT) to determine with strong confidence whether a Wi-Fi transmitter is close by (within a few centimeters). This proximity detector can be the basis for trustworthy relationships between devices. A poster paper about this idea just won the best-poster award at MobiCom 2018, and the full paper was just accepted for presentation at MobiCom 2019. See below for the abstract, or check out the corresponding three-page paper.
Authentication has become an integral part of computer usage, but it still remains an interruptive step in people’s workflow. To authenticate to a computer, depending on the authentication method, users must exert mental effort (e.g., recall their password) and/or physical effort (e.g., type their password). These factors increase the cost of context switch for users – cost of switching attention from a primary task to the authentication step and back to the task – disrupting users’ workflow. Clinical staff have often told us they are frustrated by the need to repeatedly log into their clinical desktop computers – sometimes hundreds of times in a day.
In this paper, presented by David Kotz at Ubicomp’18 in Singapore, we propose Seamless Authentication using Wristbands (SAW). SAW is an authentication method designed to address this shortcoming of proximity-based authentication methods, and we do so by adding a quick low-effort user input step that explicitly captures user intentionality for authentication. In SAW, the user’s wristband (e.g., fitness tracker, smartwatch) acts as the user’s authentication token. Read more below, and in the paper.
THaW welcomes Professor Kevin Kornegay and his students from Morgan State University in Baltimore MD. Kevin’s lab brings deep expertise in Medical IoT device security assessment, profiling, and hardening to an exploration of voice-based assistants.
Voice-assisted IoT devices such as Alexa, Siri, and Google Assistant are gaining use as portals for medical services. However, the potential safety and security issues they pose are not well understood by patients and consumers. In this collaboration, we will investigate some of the potential security issues of these devices using reverse engineering techniques to expose the vulnerabilities and propose recommendations for secure usage.
At the Joint Conference on Pervasive and Ubiquitous Computing conference, Ubicomp, David Kotz presented THaW’s work to develop a novel biometric approach to identifying and verifying who is wearing a device – an important consideration for a medical device that may be collecting diagnostic information that is fed into an electronic health record. Their novel approach is to use vocal resonance, i.e., the sound of your voice as it passes through bones and tissues, for a device to recognize its wearer and verify that it is physically in contact with the wearer… not just nearby. They implemented the method on a wearable-class computing device and showed high accuracy and low energy consumption.
Rui Liu, Cory Cornelius, Reza Rawassizadeh, Ron Peterson, and David Kotz. Vocal Resonance: Using Internal Body Voice for Wearable Authentication. Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies (IMWUT) (UbiComp), 2(1), March 2018. DOI 10.1145/3191751.
Abstract: We observe the advent of body-area networks of pervasive wearable devices, whether for health monitoring, personal assistance, entertainment, or home automation. For many devices, it is critical to identify the wearer, allowing sensor data to be properly labeled or personalized behavior to be properly achieved. In this paper we propose the use of vocal resonance, that is, the sound of the person’s voice as it travels through the person’s body – a method we anticipate would be suitable for devices worn on the head, neck, or chest. In this regard, we go well beyond the simple challenge of speaker recognition: we want to know who is wearing the device. We explore two machine-learning approaches that analyze voice samples from a small throat-mounted microphone and allow the device to determine whether (a) the speaker is indeed the expected person, and (b) the microphone-enabled device is physically on the speaker’s body. We collected data from 29 subjects, demonstrate the feasibility of a prototype, and show that our DNN method achieved balanced accuracy 0.914 for identification and 0.961 for verification by using an LSTM-based deep-learning model, while our efficient GMM method achieved balanced accuracy 0.875 for identification and 0.942 for verification.
In June, THaW’s Eric Johnson once again met with a prominent Information Security Officer to discuss the state of security in health care. Juniper Networks’ CISO Sherry Ryan met with Eric to discuss the global implications of cloud-based computing, and attacks from hostile nation states. Click above to watch the discussion in full.