# Legacy ICS Cybersecurity Assessment Using Hybrid Threat Modeling--An Oil and Gas Sector Case Study
## 2 Background and Related Work
### Threat Modeling Techniques
#### 2.2.2. STRIDE Threat Modeling  
The STRIDE [14] Method is a threat modeling methodology that identifies and categories potential system threats. Each letter in STRIDE represents a specific attack category.  
\begin{table}
\begin{tabular}{c p{284.5 pt} p{284.5 pt}} \hline \hline
**ID** & **Term** & **Meaning in PASTA** \\ \hline
3 & Weakness/ vulnerability & What an attack (supporting a threat) leverages to make its way into the system, either a tangible issue (like a badly configured firewall, cloud component, third-party framework, or RBAC model) or a poor business logic or process (lack of financial oversight on expenses). \\ \hline
4 & Use cases & Expected design behavior of the system. \\ \hline
5 & Abuse cases & Manipulation of use cases in order to yield ulterior motives of the user (e.g., bypass, injection, information leakage, etc.). \\ \hline
5 & Actor & Anything able to perform or use a use case or an abuse case. \\ \hline
7 & Attack & Any action that supports a threat motive against a target asset by exploiting a vulnerability/weakness. \\ \hline
8 & Attack vector & An interface through which an attack traverses. \\ \hline
9 & Countermeasures & Countermeasures Mitigations of a weakness that reduce the probability an attack will be successful. \\ \hline
10 & Attack surface & The set of all possible attack vectors, both logical and physical. \\ \hline
11 & Attack trees & A representation of the relationship between threats, target assets, associated vulnerabilities, Correlating attack patterns, and countermeasures. Use cases can serve as metadata associated with assets, and abuse cases similarly can serve as metadata for attack patterns. \\ \hline
12 & Impact & The direct or indirect financial value of the damage caused by an attack. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Cont.  
* Spoofing is the act of pretending to be a legitimate user or system in order to obtain unauthorized access to or alter data.
* Tampering is the act of changing code, data, or system configurations with the intention of compromising a system's integrity or introducing vulnerabilities.
* Repudiation occurs when a system or program lacks the security measures necessary to accurately monitor and record user behavior, allowing for malicious manipulation or falsifying the detection of new actions.
* Information disclosure is the unauthorized access and exposure of private or sensitive data within a system.
* Denial-of-Service (DoS) attacks prevent authorized users from accessing system resources or functionality and bring down the system's services.
* Elevation of privilege refers to gaining unapproved access or control over a system beyond the scope of authorized authorization.  
Moreover, Microsoft [28] defines threat modeling as a process that contains five steps: \"1. Defining security requirements; 2. Creating an application diagram; 3. Identifying threats; 4. Mitigating threats; and 5. Validating the mitigation of threats\".  
The proposed framework divides step 2 into two stages: creating the architecture over views and decomposing the system using a DFD diagram. Applying STRIDE to a legacy ICS system helps security experts detect a greater variety of potential attacks and weaknesses. This makes it possible to assess the security status of the system in greater detail.