Cyber-physical attacks and defences in the smart grid: a survey <s> Overview <s> Most government, industry, and academic efforts to protect the power grid have focused on information security mechanisms for preventing and detecting attacks. In addition to these mechanisms, control engineering can help improve power grid security. <s> BIB001 </s> Cyber-physical attacks and defences in the smart grid: a survey <s> Overview <s> This technical note analyzes the effect of stealthy integrity attacks on Cyber-Physical Systems, which is modeled as a Stochastic Linear Time-Invariant (LTI) system equipped with a linear filter, a linear feedback controller and a $\chi^{2}$ failure detector. An attacker wishes to induce perturbation in the control loop by compromising a subset of the sensors and injecting an exogenous control input, without incurring detection from an anomaly detector. We show how the problem can be modeled, from the attacker's standpoint, as a constrained control problem and that the characterization of the maximum perturbation can be posed as reachable set computation, which we solve using ellipsoidal calculus. <s> BIB002
In this paper, we refer to CP attack as the intrigue schemes exploiting the vulnerabilities in the CP structure of the smart grid. Although dedicated attacks on either cyber or PSs also pose threats to the system, investigation on the integrative CP attacks is an emerging yet critical topic that remains largely unclear. The interconnection of millions of field devices has created a huge attack surface while associated vulnerabilities be remotely located across the CP domains; moreover, the interfaces in-between the CP structures are also vulnerable to attacks launched from both domains. Fig. 2 illustrates a typical CP structure of smart grid. The CP loop of information and operations can be compromised at the control centres and systems, two-way communication channels, and the physical power systems. The vulnerability of this structure has been illustrated in the recent incidence of Ukraine power grid attack in 2016  : malware injected from the communication channels allowed the attacker to obtain illegal access to the control centres. The information was collected subsequently to determine the critical lines in the regional grid. Malicious commands were then sent to trip these lines that led to a widespread power blackout. The control system was further hacked to delay the restoration process. Knowledgeable attackers can directly exploit vulnerabilities of control systems to exert immediate and significant impacts in the smart grid. Depending on the target systems or policy, the impact of control-based attacks ranges from transient voltage and frequency instability, steady-state line overloading and load shedding, to massive blackouts resulting from cascading failures. An introduction to the control systems in smart grid and their attack-resilience can be found in BIB001 , and a generalised control-attack model has been developed in BIB002 . Measurement-based attacks pose another critical threat in the smart grid. Instead of directly manipulate control signals, attackers can compromise the measurements to weaken situation awareness by concealing the occurrence of disturbances or mislead control actions by reporting non-existing contingencies. Both types of attacks are within the scope of CP attacks discussed in this paper. Two types of factors are commonly considered in the design of a critical attack scheme: the cost of the attacker and the cost of the defender. For the attacker, the costs typically include the resources and knowledge required to launch the attack; in many cases, the risk of being detected is also included. For the defender or operator, the costs typically comprise from equipment damages, power outages, and economic losses. The rest of this section will unfold the attack schemes on generation, transmission, distribution, and electricity markets, respectively.