Consider a state that chooses security levels at two sites (Targets A and B), after which a terrorist chooses which site to attack (and potentially a scope of attack). The state values A more highly. If the state knows which target the terrorist values more highly, he will choose a higher level of security at this site. Under complete information, if the terrorist’s only choice is which site to attack, the state will set security levels for which the terrorist prefers to attack A over B if and only if the ratio of the value of B to the value of A is greater for the state than for the terrorist. When the state has incomplete information on the terrorist’s target values, the optimal security levels may be such that: a target is completely undefended (but attacked with positive probability); the probability of attack is greater at A than at B; and the expected damage from an attack is greater at A than at B. In total, the results reveal that the state’s choice of security is heavily influenced by the terrorist’s target valuations.
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