## 4 Defense Strategies Against Deliberate Attacks on IECPS
### Preemptive Prevention
#### 4.1.1 Redundant Equipment Planning  
When a deliberate attack occurs and some functions of IECPS are destroyed, the system's first priority is to repair the damaged functions. In order to ensure that the restoration is carried out with precision, a comprehensive assessment of the damage caused by the attack needs to be carried out to identify which system physical facilities and cyber components need to be rebuilt. Immediately after the completion of the restoration of system functions, it is necessary to carry out an investigation of the attack on the invasion method, in-depth analysis of the system vulnerabilities exploited by the attacker, and through this analysis as a breakthrough to further explore other potential vulnerabilities in the system. Finally, it is necessary to conduct a comprehensive evaluation of the defense measures, identify the weak links in the defense process, and take corresponding improvement measures to optimize and enhance the overall defense capability of the system. For IECPS, the configuration of device redundancy is a critical strategy to bolster its defense capabilities against deliberate attacks, representing a foundational approach in system design. Redundancy encompasses two interpretations: the first refers to unnecessary or superfluous components, while the second involves the deliberate duplication of critical parts. In this context, redundancy in equipment planning pertains to the latter interpretation. In energy systems, to ensure security and reliability, the deliberate duplication of key components or functions can significantly mitigate the risks associated with equipment compromise and minimize system losses following deliberate attacks. Redundant equipment planning can be classified into two categories based on the role of the redundant components: the energy equipment level and the cyber system level. At the level of energy devices, in [78], the effect of parallel connection of multiple devices to improve the safety of an integrated energy system is theoretically analyzed. In [79], the impact of a multi-energy microgrid system failure is reduced by configuring additional microturbines and solar cells. In [80], researchers proposed a redundancy planning method for combined cooling heating and power equipment based on the probabilistic analysis using a Markov model, which resulted in a significant reduction in the interruption rate of energy supply when the system suffers a fault. In addition to the redundant configuration of energy supply equipment mentioned above, the planning of energy storage devices is also an important means to improve the reliability of energy supply. In [81], the load loss of the system under extreme events is effectively reduced by rational allocation of the capacity and power of the energy storage system. In [82], a planning method for mobile energy storage in distribution networks is proposed to utilize the mobility and flexibility of mobile energy storage to improve the power supply reliability of distribution systems. In [83], the optimization method of mobile energy storage capacity under multiple line failure scenarios is further explored and the power loss status of the system is substantially improved. At the cyber level, the main protection against deliberate attacks is through the configuration of redundant measurement devices. Redundant configurations of measurement devices can, to a certain extent, maintain the data integrity of state estimation, thus resisting to reduce the risk of deliberate attacks. In [84], the relationship between the level of measurement redundancy and the risk of FDIA is revealed through criticality analysis, and graph theoretic metrics are proposed to analyze the vulnerability of the measurement system.