Efficient and Low-Cost Hardware Defense Against DNS Amplification Attacks

DNS amplification attacks utilize IP address spoofing and large numbers of open recursive DNS servers to perform the bandwidth consumption attack. During an attack, it ceaselessly fabricates DNS queries to the exploited open recursive DNS servers, and all the responses, often with larger size than the query messages, are reflected to the single victim due to the source IP address spoofing. While it is difficult to defend against this attack from the root causes by eliminating the open recursive DNS servers and IP spoofing for the whole Internet, in this paper, we take a different methodology to defend against it at the leaf router of victim´s ISP or organization. We propose an efficient and low-cost hardware approach to first detect the DNS amplification attack accurately and responsively. Once the attack is confirmed, our approach is then activated to filter out all the illegitimate DNS responses by using a two-Bloom filter solution. We demonstrate that the memory cost of our approach is feasible for the hardware implementation even up to the OC-768 link. Through trace-driven simulations, it is shown that our approach is effective in both the detecting and filtering phases.