## 2 Materials and Methods  
### Modern Cyber-Security Training Platforms  
Nowadays, a high variety of research and commercial platforms is available for cyber-security training for both individuals and organizations. A comparison of them with our method is presented in Table 1 and is detailed in [24]. Usually, most of the general-purpose e-learning platforms (e.g., Coursera (Mountain View, CA, USA, 2012-2020), Udacity (Mountain View, CA, USA, 2011-2020), edX (MA, USA, 2012-2020), etc.) offer introductory and main educational courses on cyber-security. On the other hand, specialized solutions, such as the SANS (Bethesda, MD, USA, 2000-2020) [11], CyberInternAcademy (MO, USA, 2017-2020) [12], StationX (London, UK, 1996-2020) [13], Cybrary (College Park, MD, USA, 2016-2020) [14], and AwareGO (Reykjavik, Iceland, 2011-2020) [15], support more advance and focused training. In most cases, all these approaches target individuals whose goal is to develop/sharpen new skills. However, they fail to provide hands-on experience on real systems or even cyber-ranges. Modern cyber-ranges platforms, such as BeOne (Hilversum, The Netherlands, 2013-2020) [16], ISACA's CyberSecurity Nexus (CSX) (Rolling Meadows, IL, USA, 1967-2020) [17], Kaspersky (Moscow, Russia, 1997-2020) [18], and CyberBit (Raanana, Israel, 2019-2020) [19], offer more advance features. THREAT-ARREST combines all modern training aspects of serious gaming [25; 26], emulation and simulation in a concrete manner [27], and offers continuous security assurance and programme adaptation based on the trainee's performance and skills (Table 1). The platform [24] offers training on known and/or new advanced cyber-attack scenarios, taking different types of action against them, including: preparedness, detection and analysis, incident response, and post incident response actions. The THREAT-ARREST platform supports the use of security testing, monitoring and assessment tools at different layers in the implementation stack, including:  
- Network layer tools (e.g., intrusion detection systems, firewalls, honeypots/honeynet);  
- Infrastructure layer tools (e.g., security monitors, passive and active penetration testing tools (e.g., configuration testing, SSL/TLS testing);  
- Application layer tools (e.g., security monitors, code analysis, as well as passive and active penetration testing tools such as authentication testing, database testing, session management testing, data validation and injection testing). The procedure begins by analyzing the organization's system. The Assurance Tool [28] evaluates the current security level and reports the most significant security issues that must drive the following training process. Then, hybrid training programmes are produced, and tailored to the organizational needs and the trainee types. This includes the main training material along with serious games, as well as the simulation and emulation of the cyber range system. THREAT-ARREST also provides continuous evaluation of: (a) the performance of individual trainees in specific training programmes; \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Feature** & **A** & **B** & **C** & **D** & **E** & **F** \\ \hline Automatic security vulnerability analysis of a pilot system & **Y** & **N** & **N** & **N** & **N** & **N** \\ Multi-layer modelling & **Y** & **P** & **Y** & **Y** & **Y** & **P** \\ Continuous security assurance & **Y** & **N** & **N** & **Y** & **Y** & **N** \\ Serious gaming & **Y** & **N** & **Y** & **Y** & **N** & **P** \\ Realistic simulation of cyber systems & **Y** & **P** & **Y** & **Y** & **Y** & **N** \\ Combination of emulated and real equipment & **Y** & **N** & **P** & **Y** & **N** & **N** \\
**Programme runtime evaluation** & **Y** & **N** & **N** & **Y** & **Y** & **Y** \\
**Programme runtime adaptation** & **Y** & **N** & **Y** & **Y** & **N** & **P** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cyber-security training platforms: (A) THREAT-ARREST, (B) BeOne, (C) Kaspersky, (D) ISACA CSX, (E) CyberBit, (F) online training platforms.