## 5 Case Study
### Protection Strategy Analysis
#### 5.5.1 Protection Strategy Analysis: Improving Robustness  
The optimized protection strategy for improving the robustness of the substation on a component-by-component basis is presented in Table 6, below. A mixed strategy of protection allocation to each of the components in the substation is also included, under the assumption that the protection budget will only cover for one full protection for one component in the infrastructure. It should be noted that components A and B are the most vulnerable components in the critical infrastructure system. The high value of these two components can be inferred from the large number of other components that are supported by one or both of them, as well as their relatively compact size, which renders it easier for a single attack on these components to result in high levels of damage. It also worth noting that, when the overall level of protection is reduced, a higher proportion of protection is required for component B; this indicates the paramount importance of protecting component B when seeking to reduce losses from terrorist attacks, especially under restrictive budgetary conditions. We calculated the return of investment (ROI) associated with the installation of each level of protection confronting a 20 kg TNT attack under a game-theory assumption--the ROI is calculated based on an estimated lifespan of 20 years for the infrastructure with a successful terrorist attack occurring rate of 5.78% annually (General Security Service, 2015). ROI is the Internal Rate of Return of each alternative, where the investment is the cost of the protection alternative and the return is the reduction in the risk assessment in present value. The lowest-budget loss reduction, which is defined as the expected amount by which losses are reduced (\(\Delta L\)) at the baseline protection budget \(Bg_{P}\) (a protection investment of 105,000 N.I.S according to expert estimation), is presented along with the protection ROI in Figure 3.  
It is clear from Figure 3 that the cost effectiveness of protection methods decreases when installing higher levels of protections. To achieve the most cost-effective protection strategy, lower levels of protection methods should be applied specifically to (in order of importance) components B and A. Analysis of protective arrangements in response to less severe attacking strategies, i.e., using TNT projectiles as small as 5 kg, was conducted using the same methodology described above. We found that \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Level of**} & \multicolumn{8}{c}{**Protection Allocation to Each Component**} & \multicolumn{8}{c}{**Expected Total**} & \multirow{2}{*}{**Percentage**} \\ \cline{2-2} \cline{5-11}  & **A** & & & & & & & & & & **Loss (N.I.S.)** & **Reduction in Loss** \\ \hline None & N/A & N/A & N/A & N/A & N/A & N/A & N/A & N/A & N/A & 14,291,300 & 0\% \\ I & 0.42 & 0.58 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 6,153,747 & 59\% \\ II & 0.41 & 0.59 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 6,702,103 & 53\% \\ III & 0.35 & 0.65 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 8,103,435 & 43\% \\ IV & 0.31 & 0.69 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 8,834,589 & 38\% \\ V & 0.15 & 0.85 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 10,053,180 & 30\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Protection Strategy Arrangements Aimed at Improving Robustness  
Figure 3: Comparison of ROI between Alternative Protection Levels. the most cost-effective strategy for each case was still Level V protection, and the optimized allocation of protection to each component is listed in Table 7. Our estimates for the ROI and loss-reduction proportion for each type of attack and protection method are also presented in Figure 4.  
It can be seen that the optimized protection strategy is not sensitive to the quantity of explosives used in the terrorist attack, with the effectiveness of protection remaining within a very narrow range of approximately 30% of loss reduction.