# Threat Modelling and Beyond-Novel Approaches to Cyber Secure the Smart Energy System
## 6 Attack Scenarios and Exploitation Probability Assessment
### Exploitation Probability Assessment  
In order to effectively address the different threats, and to model detected vulnerabilities, an assessment of the system components from the exploitation probability point of view is very useful. This is reflected in the fact that different vulnerabilities have different security protection mechanisms in place, and that probability to exploit such vulnerabilities differs. The risk assessment of system components outlined by [PERSON] et al. [42] was obtained by the organization responsible for the specific component. In similar approaches proposed by [PERSON] et al. [61] and [PERSON] et al. [56] exploitation probabilities were defined through extensive literature research. Their work proposes a new methodology for quantifying the likelihood of the compromise of a cyber component of SG, and includes risk assessment based on direct or indirect impact of the breach.  
In our approach, the CVSS tool is adopted for the calculation of exploitation probabilities, with certain methodology modifications compared to the existing approaches. The first step is a mapping of the components in use and their interrelation at the evaluated environment, based on the threats obtained by the threat modeling process of the specified use cases.  
The CVSS tool have several modules available, where the base score module, according to [PERSON] et al., provides a good basis for the calculation of the probability of an attack. Base score module have three sub-modules that can be used for calculating probabilities: _exploitability_, _scope_ and _impact_ sub-modules. Exploitability sub-module reflects how easily a vulnerability can be exploited, while the scope and impact sub-modules quantify the consequences of a successful exploit.  
In contrast to [62], our work takes into account, apart from exploitability of the sub-module, also the core and impact sub-modules, because in penetrating the smart grid, these impact-related parameters are also in the focus of an attacker and, therefore, should be part of the calculation.  
The _exploitability_ sub-module takes into account:  
* The attack vector--reflects the context by which a vulnerability can be exploited;
* The attack complexity--outlines how much effort in the preparation or execution of the attack against a vulnerable component the attacker have to invest;
* Privileges required--denote the level of privileges an attacker must obtain in order to successfully attack a component;
* User interaction--if another human user must be involved for a successful attack.  
The _scope_ sub-module rates if a vulnerability in one asset affects other assets, which are outside of this security authority.  
The _impact_ sub-module takes into account the CIA Triade:  
* Confidentiality--to what extent confidentiality is affected;
* Integrity--refers to the trustworthiness and correctness;
* Availability--rates the impact of a successful attack to the availability of the affected component.  
For less complex attacks, the base metric score is higher because such an attack have a higher likelihood. The score obtained from the CVSS system in range 1-10, and is normalised to the range 0-1 for further calculations. In Tables 3-5, the exploitation probabilities related to the different threats and for the different use cases are listed.