Practical Verifiable In-network Filtering for DDoS Defense
Deli Gong, Muoi Tran, Shweta Annasaheb Shinde, Hao Jin, Vyas Sekar, Prateek Saxena, Min Suk Kang · 2019
In light of ever-increasing scale and sophistication of modern distributed denial-of-service (DDoS) attacks, recent proposals show that in-network filtering of DDoS traffic at a handful of transit networks can handle volumetric attacks effectively. In this paper, we identify a subtle but important security risk in existing in-network filtering proposals. That is, a transit network may use the in-network filtering services as an excuse for any arbitrary packet drops made for its own benefit. For example, a malicious transit network may execute any filtering rules to discriminate against some of its neighboring networks based on its business preference while claiming that it is for the purpose of DDoS defense. We argue that this is due to the lack of verifiable filtering-i.e., no single party can check if a transit network executes the filter rules correctly as requested by the DDoS victims. To make in-network filtering a more robust defense primitive, we propose a verifiable in-network filtering system, called VIF, that exploits emerging hardware-based trusted execution environments (TEEs) and offers filtering verifiability to DDoS victims and neighboring networks. Our proof of concept demonstrates that a VIF filter implementation on commodity servers with TEE support can handle traffic at line rate (e.g., 10 Gb/s) and execute up to 3,000 filter rules. We show that VIF can scale to handle larger traffic volume (e.g., 500 Gb/s) and more complex filtering operations (e.g., 150,000 filter rules) by parallelizing the TEE-based filters. As a practical deployment model, we suggest that Internet exchange points (IXPs) are the good candidates to be early adopters of our verifiable filters due to their central locations and flexible software-defined architecture. Our large-scale simulations of two realistic attacks (i.e., DNS amplification, Mirai-based flooding) show that adopting VIF filtering service at only a small number (e.g., 5-25) of large IXPs is sufficient to handle the majority (e.g., up to 80-90%) of DDoS traffic.