A bilevel partial interdiction problem with capacitated facilities and demand outsourcing

► We investigate a bilevel facility interdiction problem between an attacker and defender, where the attacker is the leader who wants to cause the most disruption in a median type network and the defender tries to assign customer demand to the facilities according to the remaining capacities and outsource the unmet demand with a penalty. ► Partial interdiction is possible where a partially interdicted facility loses some of its capacity in proportion to the attack level. ► Two solution methods are proposed. The first is a progressive grid search heuristic that can be applied for instances with up to 10 facilities. The second is a multi-start revised simplex search procedure. Both of the heuristics call Cplex to optimally solve an integer programming model in the lower level problem. ► We evaluate the benefit of the partial interdiction approach over full interdiction from the attacker's point of view.