# Cybersecurity and Safety Co-Engineering of Cyberphysical Systems--A Comprehensive Survey
## 2 Related Work  
### Previous Reviews  
There are two types of reviews; _narrative_ and _systematic_ reviews [9]. _Narrative_ reviews aim to identify studies in the literature that describe a specific problem of interest. In such reviews, systematic guidelines regarding the searching method, the identification of research questions, and the screening process are not considered. Thus, such reviews do not provide a comprehensive understanding of the stated problem. _Systematic_ reviews are methodical approaches to identify, analyze, and criticize the results concerning predefined research questions. Such reviews aim to provide inclusive results regarding a well predefined problem with specific research questions. Specific processes and guidelines exist for conducting a systematic literature review, including on how to formulate the research questions; research the literature; screen and select the results; and analyze and document the conclusions. A total of six reviews of joint safety and security analysis methods have been identified in the recent literature. Of those five, References [3; 4; 5; 6; 8] are narrative and only one [7] is systematic. Even though the total number of methods reviewed therein is 60, surprisingly, the intersection of the set of methods reviewed in Reference [7] and of the set of methods reviewed in all other reviews counts only seven elements. [PERSON] et al. [3] conducted a survey of various safety and security approaches and studied the potential adoption of a safety approach for security analysis and vice versa. Although this work provides insight into safety and security concepts by analyzing the relevant terminology, the methods that are surveyed are not combined approaches but traditional safety and security methods. Specifically, safety standards along with hazard and risk analysis methods on one hand, and vulnerability and threat analysis methodologies on the other have been studied. The surveyed methods have been classified according to type (_safety to security_ or _security to safety_); according to the approach taken (_Architectural concepts_, _Graphical modeling_, _structured risk assessment_, _and Testing_); and according to safety characteristics (_fault prevention_, _fault tolerance_, _fault removal_, _and fault forecasting_). [PERSON] et al. [4] provide a survey of approaches combining safety and security risk analysis for industrial infrastructures. Thirty nine methods were analyzed and grouped considering various criteria: the way each method treats safety and security (_unification/integration or harmonization_); the lifecycle phase (_operational/requirements or design_) in which the studied system is; and the type of the risk assessment approach (_quantitative/qualitative_). The methods are classified into _generic_ and _model-based_. Methods in the former group describe the lifecycle stages and the sequence of activities in each stage, whereas the latter includes _graphical or non-graphical_ methods, that may be supported by software tools. Furthermore, an overview of the safety and security standards for industrial infrastructures is presented. Finally, by analyzing the safety and security dependencies and interdependencies, the authors concluded that safety and security are complementary and should be treated jointly to improve the risk assessment process. [PERSON] et al. [5] surveyed several integrated safety and security risk assessment methods and identified their key characteristics. The analysis was performed considering five criteria: First the identified approaches were classified according to the number of the _citations_ that they had received in the scientific literature. The authors argue that the research community started to recognize the importance of the combination of safety and security analyses in 2014 and 2015, with the most prominent methods being the Extended Fault Tree (EFT) and the Extended Component Fault Tree (E-CFT). Additionally, the approaches were grouped according to the steps involved in the risk assessment process.