Mingkui Wei

Greenbench: A benchmark for observing power grid vulnerability under data-centric threats

Smart grid is a cyber-physical system which integrates communication networks into traditional power grid. This integration, however, makes the power grid susceptible to cyber attacks. One of the most distinguished challenges in studying the aftermath of cyber attacks in smart grid lies in data-centric threats. Even though such attacks are critical to the information network, they will result in much more Domino-like impact than they behave in cyber world. This is because for an information-centric network, distorted or delayed information undermines services and applications. But in power grid, these data-centric attacks may result in instable power systems, and further detrimental impact of power supplies. In this paper, we present Greenbench, a benchmark that is designed to evaluate real-time power grid dynamics in response to data-centric attacks. The simulation results provide several counter-intuitive suggestions to both smart grid security research and deployment.

On detection and concealment of critical roles in tactical wireless networks

In tactical wireless networks, the one-to-multiple communication model is pervasive due to commanding and control requirements in mission operations. In such networks, the roles of nodes are non-homogeneous; i.e., they are not equally important. This, however, opens a door for an adversary to target important nodes in the network by identifying their roles. In this paper, we investigate an important open question: how to detect and conceal the roles of nodes in tactical wireless networks? Answers to this question are of essential importance to understand how to identify critical roles and prevent them from being the primary targets. We demonstrate via analysis and simulations that it is feasible and even accurate to identify critical roles of nodes by looking at network traffic patterns. To provide countermeasures against role detection, we propose role concealment methods based on proactive network strategies. We use simulations to evaluate the effectiveness and costs of the role concealment methods.

Combat the disaster: Communications in smart grid alleviate cascading failures

Cascading failure is one of the most catastrophic events in power grid, which refers to large scale power system outage caused by the rampant spread of small scale system fault or even single device failure. Its disastrous result is expected to be mitigated in the scope of smart gird, in which communication enabled smart devices exchange critical information to preclude such events. To carry the concept into reality, one pivotal step is quantitative study of the benefit smart grid can bring, i.e., to what extent smart grid can improve power system stability, specifically, in combating cascading failure? We identify three aspects, time, space, and scale, which are needed for thorough evaluation of the impact of a cascading failure, and further propose a new cascading failure model which is able to depict all three aspects with numerical results. Our observations explicitly suggest that communication between power devices is essential in alleviating the impact of cascading failure, and that even a basic information exchange among limited number of power devices could significantly ameliorate the aftermath of a cascading failure in power grid.

How they interact? Understanding cyber and physical interactions against fault propagation in smart grid

In the smart grid, computer networks (i.e., the cyber domain) are built upon physical infrastructures (i.e., the physical domain) to facilitate advanced functionalities that were considered not possible in legacy systems. It is envisioned that such a cyber-physical paradigm enables intelligent, collaborative controls to prevent faults from propagating along large-scale infrastructures, which is a primary cause for massive blackouts (e.g., Northeast blackout of 2003). Despite this promising vision, how effective cyber and physical interactions are against fault propagation is not yet fully investigated. In this paper, we use analysis and system-level simulations to characterize such interactions during load shedding, which is a process to stop fault propagation by shedding a computed amount of loads based on collaborative communication. Specifically, we model faults happening in the physical domain as a counting process, with each count triggering a load shedding action on the fly in the cyber domain. We show that although global load shedding design is considered optimal by globally coordinating shedding actions in power engineering, its induced failure probability (defined as the one that at least a given number of power lines fail) is scalable to the delay performance and the system size in the cyber domain, thus less likely to stop fault propagation in large systems than local shedding design that sheds loads within a limited system scope. Our study demonstrates that a joint view on cyber and physical factors is essential for failure prevention design in the smart grid.

Safety Can Be Dangerous: Secure Communications Impair Smart Grid Stability under Emergencies

Smart grid features real-time monitoring and control by integrating advanced communication networks into traditional power grids. This integration, however, makes smart grid vulnerable to cyber attacks, i.e., the anomalies caused by attackers in the communication network can affect ordinary operations of the power grid and result in severe physical damage. To protect smart grid from cyber attacks, many traditional countermeasures, such as message encryption, have been proposed to be directly migrated to fit this system. In this regard, the very first fundamental questions that need to be addressed are how to evaluate and compare the physical impacts of cyber attacks and countermeasures, and whether traditional cyber security countermeasures can result in satisfactory performance in smart grid. Motivated by these questions, we establish a small-scale smart grid prototype, and use both experiments and cross-domain simulations to evaluate and compare the reaction of the power system under cyber attacks, with and without the presence of traditional countermeasures. Our study reveals that traditional countermeasures can not be readily migrated to protect smart grid in particular, and shows that during system emergencies where prompt system reactions are critical, the extra latency caused by message encryption and decryption can result in more than 10 times in the magnitude of voltage collapse. Our work indicates that traditional countermeasures may not fit smart grid, the newly emerging cyber- physical system, which has strict time constraint. Therefore it is essential for researchers to seek solutions to address smart grid specific security threats.

Claim What You Need: A Text-Mining Approach on Android Permission Request Authorization

Android is one of the most popular mobile operating systems nowadays, whose popularity, however, also attracts even more crafty developers to develop malicious softwares, or malwares, to exploit illegitimate means for profit. As a basic countermeasure, Android enforces the permission request scheme, in which an application (App) is required to present to the user the system resources (permissions) it will access, and ask users approval before installation. However, this approach has been proven ineffective as it delegates the whole responsibility of decision- making to the user, who usually lacks the professional knowledge to comprehend the interpretation of a permission. Alternatively, many current researches focus on identifying potential malwares based on attributes of individual Apps, such as inspecting their source code, which, unfortunately, fall in another extreme which tend to make the decision for the user. Nevertheless, from the users perspective, a satisfactory solution should be an approach which assists users to make the decision of the App installation on their own, by providing them with lucid reasons and requiring minimum professional knowledge. Based on the observation that the description of an App is the most direct interface to communicate its functionality to the user, in this paper we are motivated to explore the relationship between the description and the requested permissions of an App, and further build a model to predict proper permissions based on its description. Our evaluation with Apps collected from the Google Play Market shows that our prediction can achieve as high as 87% accuracy. In this regard, provide a user has full understanding of the description of an App, our model can act as an effective reminder to the user if the App tries to stealthily request permissions that are inconsistent with its description, which is a major character commonly exploited by malwares.

On modeling and understanding vehicle evacuation attacks in VANETs

To secure a Vehicular Ad-hoc Network (VANET), extensive studies have been conducted on developing authentication infrastructures, and identifying misbehaving vehicles. The effectiveness of such efforts heavily depends on the underlying communication network. However, information exchange in the VANET can be severely delayed because of its highly-dynamic and partially-connected topology. Such delay can be potentially exploited by attackers to cause physical impacts to the transportation system. In this paper, we propose and model a new attack, called vehicle evacuation attack, to investigate how the message delay endangers the trustworthiness in VANETs, and further causes physical impacts to cars on the road. Our study demonstrates that there exists a linear relationship between the delay of message dissemination and the impact of the vehicle evacuation attack, which can be used as a guideline on security, reliability, and safety design in real-world VANETs.

On Characterizing Information Dissemination During City-Wide Cascading Failures in Smart Grid

Although the smart gird is expected to eliminate cascading failures with the help of real-time system monitoring and control, it is yet unknown whether its underlying communication network is fast and reliable enough to achieve this goal. In this paper, we take an in-depth study on this issue by addressing three specific questions: 1) what is the evolution process of information dissemination and fault propagation in the smart grid?; 2) how to quantify the impact of cascading failures?; and 3) what are the conditions that information dissemination becomes either a booster or an adversary in mitigating cascading failures? To answer these questions, we build an innovative framework, the cascading failure with communications framework, to consolidate both communication networks and power grids, and provide quantitative evaluation on the impact of cascading failures. By studying and observing the progress of cascading failures in two city-wide power grids, we find that information dissemination is not always the winner in the race against fault propagation. Particularly, while fast and reliable communications can help in mitigating the consequences of cascading failures, anomalies such as massage delays may weaken its capability. Moreover, severely under-achieved communications, counter-intuitively, can even exacerbate the consequence of cascading failures.

Dominoes with communications: On characterizing the progress of cascading failures in Smart Grid

Cascading failures are one of the most devastating forces in power systems, which may be initially triggered by minor physical faults, then spread with Domino-like chain-effect, resulting in large-scale blackout. How to prevent cascading failures becomes imperative, as our daily lives heavily depend on stable and reliable power supply. The next-generation power system, namely Smart Grid, is envisioned to facilitate real-time and distributed control of critical power infrastructures, thus effectively forestalling cascading failures. Although cascading failures have been well investigated in the literature, most studies were confined only in the power operation domain with the assumption that communication is always perfect, which is, however, not true for todays communication networks, where traffic congestion and random delay happen. Therefore, an open question is how to characterize cascading failures in the communication-assisted smart grid? To this end, we take an in-depth inspection of cascading failures in smart grid and reveal the interactions between the power system and the communication network. Our results provide insights into the interactions between physical failure propagation and communication message dissemination. In addition, we show that while ideal communications can undoubtedly help prevent cascading failures, under-achieved communications (i.e., communications with severe delay) can, counter-intuitively, exacerbate cascading failures.

A Proactive and Deceptive Perspective for Role Detection and Concealment in Wireless Networks

In many wireless networks (e.g., tactical military networks), the one-to-multiple communication model is pervasive due to commanding and control requirements in mission operations. In these networks, the roles of nodes are non-homogeneous; i.e., they are not equally important. This, however, opens a door for an adversary to target important nodes in the network by identifying their roles. In this chapter, we focus on investigating an important open question: how to detect and conceal the roles of nodes in wireless networks? Answers to this question are of essential importance to understand how to identify critical roles and prevent them from being the primary targets. We demonstrate via analysis and simulations that it is feasible and even accurate to identify critical roles of nodes by looking at network traffic patterns. To provide countermeasures against role detection, we propose role concealment methods based on proactive and deceptive network strategies. We use simulations to evaluate the effectiveness and costs of the role concealment methods.