Security assessment of audience response systems using software defined radios

Audience response systems, also known as clickers, are used at many academic institutions to offer active learning environments. Since these systems are used to administer graded assignments, and sometimes even exams, it is crucial to assess their security. Our work seeks to exploit and document potential vulnerabilities of clickers. For this purpose, we use software defined radios to perform eavesdropping attacks on an audience response system in production. The results of our study demon- strate that clickers are easily exploitable. We build a prototype and show that it is practically possible to covertly steal answers from a peer or even the entire classroom, with high levels of confidence. As a result of this study, we discourage using clickers for high-stake assessments, unless manufacturers provide proper security protection.http://people.bu.edu/staro/MIT_Conference_Khai.pdfAccepted manuscrip

Cascading attacks in Wi-Fi networks: demonstration and counter-measures

Wi-Fi (IEEE 802.11) is currently one of the primary media to access the Internet. Guaranteeing the availability of Wi-Fi networks is essential to numerous online activities, such as e-commerce, video streaming, and IoT services. Attacks on availability are generally referred to as Denial-of-Service (DoS) attacks. While there exists signif- icant literature on DoS attacks against Wi-Fi networks, most of the existing attacks are localized in nature, i.e., the attacker must be in the vicinity of the victim. The purpose of this dissertation is to investigate the feasibility of mounting global DoS attacks on Wi-Fi networks and develop effective counter-measures. First, the dissertation unveils the existence of a vulnerability at the MAC layer of Wi-Fi, which allows an adversary to remotely launch a Denial-of-Service (DoS) attack that propagates both in time and space. This vulnerability stems from a coupling effect induced by hidden nodes. Cascading DoS attacks can congest an entire network and do not require the adversary to violate any protocol. The dissertation demonstrates the feasibility of such attacks through experiments with real Wi-Fi cards, extensive ns-3 simulations, and theoretical analysis. The simulations show the attack is effective both in networks operating under fixed and varying bit rates, as well as ad hoc and infrastructure modes. To gain insight into the root-causes of the attack, the network is modeled as a dynamical system and its limiting behavior is analyzed. The model predicts that a phase transition (and hence a cascading attack) is possible when the retry limit parameter of Wi-Fi is greater or equal to 7. Next, the dissertation identifies a vulnerability at the physical layer of Wi-Fi that allows an adversary to launch cascading attacks with weak interferers. This vulnerability is induced by the state machine’s logic used for processing incoming packets. In contrast to the previous attack, this attack is effective even when interference caused by hidden nodes do not corrupt every packet transmission. The attack forces Wi-Fi rate adaptation algorithms to operate at a low bit rate and significantly degrades network performance, such as communication reliability and throughput. Finally, the dissertation proposes, analyzes, and simulates a method to prevent such attacks from occurring. The key idea is to optimize the duration of packet transmissions. To achieve this goal, it is essential to properly model the impact of MAC overhead, and in particular MAC timing parameters. A new theoretical model is thus proposed, which relates the utilization of neighboring pairs of nodes using a sequence of iterative equations and uses fixed point techniques to study the limiting behavior of the sequence. The analysis shows how to optimally set the packet duration so that, on the one hand, cascading DoS attacks are avoided and, on the other hand, throughput is maximized. The analytical results are validated by extensive ns-3 simulations. A key insight obtained from the analysis and simulations is that IEEE 802.11 networks with relatively large MAC overhead are less susceptible to cascading DoS attacks than networks with smaller MAC overhead

Brief announcement: passive and active attacks on audience response systems using software defined radios

Audience response systems, also known as clickers, are used at many academic institutions to offer active learning environments. Since these systems are used to administer graded assignments, and sometimes even exams, it is crucial to assess their security. Our work seeks to exploit and document potential vulnerabilities of clickers. For this purpose, we use software defined radios to perform jamming, sniffing and spoofing attacks on an audience response system in production, which provide different possible methods of cheating. The results of our study demonstrate that clickers are easily exploitable. We build a prototype and show that it is practically possible to covertly steal or forge answers of a peer or even an entire classroom, with high levels of confidence. Additionally, we find that the receivers software of the system lacks protection against unexpected answers, which allows our spoofer to submit any ASCII character and opens the receiver up to possible fuzzing attacks. As a result of this study, we discourage using clickers for high-stake assessments, unless they provide proper security protection..http://people.bu.edu/staro/SSS2017_Brief_v0.pdfhttp://people.bu.edu/staro/SSS2017_Brief_v0.pdfhttp://people.bu.edu/staro/SSS2017_Brief_v0.pdfAccepted manuscrip

High-Frequency Observations of Cyanobacterial Blooms in Lake Taihu (China) from FY-4B/AGRI

China’s FY-4B satellite, launched on 3 June 2021, is a new-generation geostationary meteorological satellite. The Advanced Geosynchronous Radiation Imager (AGRI) onboard FY-4B has 15 spectral channels, including 2 visible (470 and 650 nm), 1 near infrared (825 nm), and 3 shortwave infrared (1379, 1610, and 2225 nm) bands, which can be used to observe the Earth system with the highest spatial resolution of 500 m and 15 min temporal resolution. In this study, FY-4B/AGRI observations were applied for the first time to monitor cyanobacterial blooms in Lake Taihu, China. The AGRI reflectance at visible and near-infrared bands was first corrected to surface reflectance using the 6S radiative transfer model. Due to the similar spectral reflectance characteristics to those of land-based vegetation, the normalized difference vegetation index (NDVI) and some other remote sensing vegetation indices are usually used for the retrieval of cyanobacterial blooms. The fractional vegetation cover (FVC) of algae, defined as the fraction of green vegetation in the nadir view, was adopted to depict the status and trend of cyanobacterial blooms. NDVI and FVC, the two remote sensing indices developed for the retrieval of land vegetation, were used for the detection of cyanobacteria blooms in Lake Taihu. Finally, the FVC derived from AGRI measurements was compared with that obtained from the Advanced Himawari Imager (AHI) onboard the Himawari-8 satellite to validate the effectiveness of our method. It was found that atmospheric correction can substantially improve the determination of the normalized difference vegetation index (NDVI) values of cyanobacterial blooms in the lake. As a proof of the robustness of the algorithm, the NDVIs are both derived from both AGRI and AHI and their magnitudes are similar. In addition, the distribution of cyanobacterial blooms derived from AGRI FVC is highly consistent with that derived from FY-3D/MERSI and EOS/MODIS. While a lower spatial resolution of FY-4B/AGRI might restrict its capability in capturing some spatial details of cyanobacterial blooms, the high-frequency measurements can provide information for the timely and effective management of aquatic ecosystems and help researchers better quantify and understand the dynamics of cyanobacterial blooms. In particular, AGRI can provide greater details on the diurnal variation in the distribution of cyanobacterial blooms owing to the high temporal resolution

Comparative pilot study on the effects of pulsating and static cupping on non-specific neck pain and local skin blood perfusion

Objective: To compare the effects of pulsating and static cupping on non-specific neck pain and local skin microcirculation blood perfusion, which is a pilot study. Methods: Seventy participants with non-specific neck pain were randomized to the following groups: low-frequency pulsating cupping (LF, n = 20); high-frequency pulsating cupping (HF, n = 20); static cupping (SC, n = 20), or waiting list (WL, n = 10). The LF, HF, and SC received a bilateral 10-minute cupping treatment at Jianzhongshu (SI 15). Outcomes were pain intensity (visual analog scale, VAS), functional status (Neck Disability Index, NDI), and skin blood perfusion at the SI 15, Dazhui (GV 14), and Shenzhu (GV 12) acupoint areas, measured using Laser Speckle Contrast Analysis technology. Results: Both LF and HF groups showed a significant reduction in VAS scores compared with the SC group (9.00, 95% CI 1.05–16.95, P = .027; 8.75, 95% CI 0.80–16.70, P = .031). There was no significant difference in VAS scores between the LF and HF groups (P > .05) and between NDI scores measured 3 days after intervention among the four groups (P > .05). In the SI 15 area, blood perfusion in the three treatment groups was higher than that in WL group (P < .01), and the perfusion unit (PU) of the HF pulsating group at 5 minutes after intervention was significantly higher compared with the SC group (P < .05). In the GV 14 area, blood perfusion in the two pulsating cupping groups was higher compared with the WL and SC groups after cupping (P < .05). In the GV 12 area, the PU of the LF group was higher compared with the other three groups only at the time of cup removal (P < .05). Conclusion: This study showed that pulsating cupping may have more favorable analgesic effects on non-specific neck pain compared with static cupping, which may be related to its better effect on improving the local skin blood perfusion. Keywords: Pulsating cupping, Static cupping, Non-specific neck pain, VAS, Blood perfusio

Variation in Melatonin Contents and Genetic Dissection of Melatonin Biosynthesis in Sesame

In recent years, people have become increasingly interested in bioactive molecules in plants that are beneficial to human health, and melatonin (N-acetyl-5-methoxytryptamine) has attracted research attention due to its excellent performance. In this study, the content of melatonin in oilseeds was investigated. From the results, it was found that sesame is an important natural food source of melatonin intake. Furthermore, the variation in melatonin content was explored in a natural sesame population, and its contents varied from 0.04 to 298.62 ng g&minus;1. Through a genome-wide association study (GWAS), a candidate gene SiWRKY67 was screened that regulates melatonin content in sesame. The sesame hairy root transformation system was developed and used to verify this gene, and it was found that the overexpression of SiWRKY67 could positively promote the melatonin content in the hairy roots. Our results provide not only a foundation for understanding the genetic structure of melatonin content in sesame seeds but also a reference for the marker-assisted breeding of sesame varieties with high melatonin content