ATTACKING DDOS AT THE SOURCE

Distributed denial-of-service (DDoS) attacks present an
Internet-wide threat. We propose D-WARD, a DDoS defense
system deployed at source-end networks that autonomously
detects and stops attacks originating from these
networks. Attacks are detected by the constant monitoring
of two-way traffic flows between the network and the rest
of the Internet and periodic comparison with normal flow
models. Mismatching flows are rate-limited in proportion
to their aggressiveness. D-WARD offers good service to legitimate
traffic even during an attack, while effectively reducing
DDoS traffic to a negligible level. A prototype of the
system has been built in a Linux router. We show its effectiveness
in various attack scenarios, discuss motivations for
deployment, and describe associated costs.


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