  We consider a new class of multi-period network interdiction problems, where
interdiction and restructuring decisions are decided upon before the network is
operated and implemented throughout the time horizon. We discuss how we apply
this new problem to disrupting domestic sex trafficking networks, and introduce
a variant where a second cooperating attacker has the ability to interdict
victims and prevent the recruitment of prospective victims. This problem is
modeled as a bilevel mixed integer linear program (BMILP), and is solved using
column-and-constraint generation with partial information. We also simplify the
BMILP when all interdictions are implemented before the network is operated.
Modeling-based augmentations are proposed to significantly improve the solution
time in a majority of instances tested. We apply our method to synthetic
domestic sex trafficking networks, and discuss policy implications from our
model. In particular, we show how preventing the recruitment of prospective
victims may be as essential to disrupting sex trafficking as interdicting
existing participants.
