In this talk, Professor Laura Albert will discuss how to protect critical information technology (IT) infrastructure using industrial and systems engineering methods. Critical IT infrastructure is vulnerable to risks that can be introduced from supply chains, and therefore, there is a need to design plans to mitigate these risks. In this research, we propose new optimization models and network interdiction models to identify a combination of cost-effective mitigations that maximally delay supply chain attacks when there exist multiple adversaries and that capture the interaction between a defender and multiple attackers. We propose network interdiction models for protecting critical infrastructure that prioritizes cost-effective security mitigations to maximally delay adversarial attacks. We consider attacks originating from multiple adversaries, each of which aims to find a “critical path” through the attack surface to complete the corresponding attack as soon as possible.