The Internet was designed to operate in a benign environment. Its original design contains few tools for resource accountability. Today, as the Internet is expanded to society at large, this lack of accountability manifested itself in many undesirable ways. One of them is the Internet's vulnerability to distributed Denial of Service (DDoS) attacks. An attacker that controls a large botnet can knock almost any site offline. This problem raises a fundamental question: can we design a network that is open, effective, and resilient to misbehaviors? In this talk, I will describe our work on designing network architectures that are resilient to DDoS attacks and how to adapt the key architectural components to today's Internet for immediate benefits.