Malicious entities may use hazardous materials as a weapon by hijacking a vehicle and transporting it to a desired target. This work presents a methodology to identify possible hijacked vehicles’ routes to vulnerable targets, assuming that probabilities of interception by law enforcement agents depend on the investment in defense resources. The methodology to identify hijacked vehicles’ routes incorporates the dual objectives of minimizing probabilities of capture and maximizing consequences if law enforcement agencies attempt to intercept the vehicle before it reaches the target. Mathematical programming models are presented to find such routes as well as the allocation of defense investments on a network.FONDECYT260FONDECYT