# Security Threats in Intelligent Transportation Systems and Their Risk Levels
## 3 Risk Analysis Study
### Risk Analysis Study in ITSs
#### 3.1.5 Risk Analysis  
TVRA methodology (ETSI, 2011) calculates the risk of identified threats using estimated values for the likelihood of occurrence and impact of threat to the system using the formula: Risk = Likelihood * Impact ([PERSON] et al., 2012). The risk is computed as the product of the numerical values of the likelihood and impact. The classes in which the risk is considered relevant are defined as: Critical (9,6)--countermeasures must be designed without delay; Major (4)-- the threat will potentially need attention; Minor (3,2,1)--the threat can be ignored in the short term (cf. Table 3). We used the definitions provided in ETSI (2003) to further break down the likelihood component into its two natural components: the technical difficulty in carrying out the threat and the motivation or potential gain on the part of the attacker for him or her to proceed. The values for technical difficulty (needed capabilities) can be defined in terms of whether or not the threat has previously been considered in theory or in practice. The following factors are assessed during the analysis to identify the weight of the attack potential required to exploit a vulnerability: system knowledge, time, expertise, opportunity and facilities. We define four levels for needed capabilities, according to [PERSON] et al. (2012): no rating (4); basic (3); moderate (2); extensive (1). The levels for motivation include: High--significant gains for attacker; Moderate--service disruption only; Low--no significant \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Attack** & **Asset** & **Vulnerability** & **Threat** & **Solution** & **Violated Security Requirement** \\ \hline Jamming attacks at vehicle level & Vehicle & OBU vulnerabilities & Unauthorized manipulation of the routing table & Frequency hopping: multiple radio transceivers & Availability \\ \hline Jamming attacks & Information & Vulnerabilities of OBU; unsecured wireless communication channel & Prevents vehicles from receiving sensitive information and using network services & Assign IP addresses when forwarding the message ([PERSON] et al., 2013); DJAVAN ([PERSON] et al., 2015) & \\ \hline Malware integration & Vehicle/vehicle user & Software fault (weak message propagation algorithm) & Leakage of sensitive private information & Update the antivirus; sandbox approach ([PERSON] et al., 2010) & Availability/ authentication \\ \hline MITM attacks & Information & Unencrypted messages; unsecured wireless communication channel & Editing message with incorrect and compromised messages & Strong cryptographic techniques ([PERSON] and [PERSON], 2013) & Availability \\ \hline MITM attacks & Infrastructure between RSU and content entity & Infrastructure communication & Hardware malfunction; software defects; unencrypted communication channel and the central entity & Modifications of messages transmitted to other vehicles via RSU and the central entity & Strong cryptographic techniques ([PERSON] et al., 2014) & Availability \\ \hline JellyFish/ intelligent cheater & Information & Vulnerabilities of end-to-end congestion control protocols & Disorder, delay or periodically drop packets that are supposed to be transmitted & End-to-end control mechanisms with long-term monitoring & Availability \\ \hline Flooding attacks & Vehicle/ infrastructure & Unsecured wireless communication channel & Network resources are no longer available to legitimate users & Flood-resilient broadcast authentication for VANET ([PERSON] et al., 2014) & Availability \\ \hline Blackhole attack & Information & Unsecure communication protocols & Prevents vehicles and infrastructure from receiving important messages and alerts & Watchdog mechanism ([PERSON] et al., 2017), Trust model based on weights ([PERSON] et al., 2011) & Availability \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Attacks targeting availability. gains (cf. Table 4).