Challenges and Principles of DDoS Defense

Distributed denial-of-service (DDoS) attacks present an Internet-wide threat. Such attacks depend on large numbers of compromised machines, but solving the problem by completely securing every machine on the Internet is impossible. Solutions located near the victim are subject to congestion and are unable to differentiate between legitimate and attack traffic, while solutions at the source-end networks cannot detect all attacks and are not effective unless widely deployed. Infrastructural approaches are promising, but will face tremendous challenges in popular acceptance and deployment. We argue that solutions to the DDoS problem must be carefully designed to meet certain fundamental principles of security and system design. These principles include using distributed solutions to solve distributed problems, avoiding security solutions that harm legitimate activities, securing a defense system from external and internal threats, having a practical strategy for adoption and completeness. We show how violations of these principles lead to limitations and weaknesses in existing approaches. We then present an example DDoS defense system that adheres to these principles—the Defensive Cooperative Overlay Mesh (DefCOM).