## 1 Introduction
### Cyber Exercises  
Like all IT systems, the food supply chain is vulnerable to cyber security threats, e.g., in the areas of smart farming and cyber-physical systems [9]. Cyber attacks against food supply chains can be devastating. Therefore, preparing for such scenarios in a safe environment is important. An effective solution to enhance the knowledge and skills of staff members against cyber threats is the cyber security exercise, where the learning audience participates in a realistic scenario using a technical infrastructure that mirrors the systems and networks in the real world [10]. Such technical infrastructure is called cyber range and/or cyber arena, especially when an expansive environment is considered. [PERSON] and [PERSON] introduce the requirements for cyber arena environments [11]: (i) realism, (ii) isolated and controlled environment, (iii) internet simulation, (iv) user and network traffic generation, (v) attack execution and simulation, (vi) organizations' infrastructures, (vii) collaboration, and (viii) planning, executing, monitoring, and analyzing. When creating new target domains for cyber arenas, the requirements of realism, user and network traffic generation, and organizations' infrastructures in particular become essential.  
Cyber arenas need services that replicate the real-world environments where the staff members would face realistic cyber attacks. One way of replicating the food supply chain is to create a digital twin, which mirrors the production cycle and factory setups of the domain. Digital models such as digital twins have their roots in life-cycle management, with a focus on computational modeling; they are virtual representations mirroring physical systems [12]. These models are, naturally, software programs that copy the behavior of their real-world counterparts. The exact definition of a digital twin is an elusive concept that is perhaps not enough distinguished from computing models and simulations [13].  
Figure 2 illustrates a typical cyber exercise conducted in a cyber arena. Domain expertise defines the scenario, which can be realized with digital twins and models. The white team (WT), also known as exercise control, controls the planning and execution of the exercise. The blue team (BT) is the learning audience of the exercise defending their systems: by implementing required incident response and forensics maneuvers, for example. The BT is usually modeled in accordance with real organizational structures, and there can be one or several BTs in the exercise. The red team (RT) acts as the threat actor by executing real cyber attacks against the exercise assets of the BTs [14; 15]. There is also a green team (GT); they act as system administrations for the whole exercise environment. Basically, the GT enable the technical exercise and assist the other teams if there are out-of-scenario technical issues during the exercise. In this paper, the domain is the food supply chain, the organizations are companies in that domain, and the Realistic Global Cyber Environment (RGCE) [16] serves as the cyber arena.  
The cyber arena models the whole networked information security infrastructure required for the cyber exercise. Consequently, it can be realized using digital twins, which meet the requirements set by cyber security exercises. Themes related to digital twins, such as physical and virtual processes and virtual environments [17], are relevant in the cyber arena.  
Figure 1: Food supply chain.