# Cyber Resilience and Incident Response in Smart Cities: A Systematic Literature Review
## 3 Results Analysis and Discussion
### Key Themes
#### 3.3.2 Cyber Resilience Analysis
The author in reference [102] argued that the key difference between control and information technology (IT) systems is the control systems' interaction with the physical world and concludes that to withstand cyberattacks, systems should be resilient by design. The author asserts that the risk to control systems is higher due to the exposure and availability of vulnerabilities combined with the increasing motivations and capabilities of the attackers. The paper focuses on sensor attacks and addresses ways of prioritising sensors. Attack types were studied using the Tennessee-Eastman process control system (TE_PCS) model [106]. An automatic response mechanism was introduced based on various system states taking into consideration a false alarm response. The author's main conclusion was the strength of the TE-PCS's design resilience. Although the proposed principles and techniques could be applied to other physical processes and the false positive rate at 1000 simulation cycles was 0%, the automated response may not be appropriate for all control systems. The author cautions of a likely lack of resilience-by-design in large scale control systems which could remain vulnerable to several attack vectors. Further, the author in reference [104] defined a trustworthy service as one which secures against cyberattacks and operates normally despite faults or attacks. The authors proposed an IoT framework to integrate smart water systems (SWSs) with the IoT using a multilayer architecture trustworthy service and proposed that security issues should be addressed systematically by developers during the design and development of each IoT layer. Anomaly behaviour analysis (ABA) intrusion detection system (IDS) methodology was applied to protect the secure gateway from attacks utilising the Smart Water System Testbed. The secure gateway is part of the communication layer. The general detection rate of the ABA-IDS approach was over 90% for 600 packets/second intensity, with less than 3.5% recorded false alarm rate, with the fastest detection of 1 s and the slowest detection of a 4 s interval. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Year** & **Primary Study** & **Smart Sector** \\ \hline
2011 & [102] & Infrastructure \\
2012 & & \\
2013 & & \\
2014 & [52] & Energy \\
2015 & [103] & Mobility—Automotive \\
2016 & & \\
2017 & [104] & Infrastructure \\
2018 & [101,105] & Energy, Mobility—Aviation \\ Q1 2019 & [40,99,100] & Security, Mobility—Aviation \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Primary studies focusing on aspects of cyber resilience(-by-design). Other studies [52, 101] focused on CNI such as power grids whilst urban systems were investigated by reference [40]. In reference [52], the resilience of five classical routing protocols applied in distributed large-scale networks was studied through simulation. Resilient techniques using route diversification were introduced to enhance the protocols' resilience against cyberattacks. The resilience was evaluated based on metrics consisting of five performance parameters which showed promising results. The communication layer was also the focus of [101] study, which proposed a new metric system framework to assess the reliability of large-scale distributed power systems. The author asserts the importance of combining the communication layer's cyber vulnerabilities with the physical layers' resilience for a meaningful assessment of the system sustainability. The following study [40] developed a network efficiency and resilience evaluation method for intelligent transportation systems (ITSs) in response to random and targeted attacks in urban areas. The author maintains that although the use of sensors is beneficial for automation, the infrastructure through their use becomes complex and liable to unknown and little understood vulnerabilities. The article concludes that the system's relative resilience was not sensitive to the levels of disruption.