Beat - An Acoustics Inspired DDoS Attack

This post details the 'Beat' attack, a unique ACK DDoS attack inspired by acoustic beat phenomena, which targeted a Magic Transit customer. It explains the mathematical basis of the attack's wave-shaped packet rate, reverse-engineers the attacker's likely equation, and describes how Cloudflare's 'flowtrackd' system, a unidirectional TCP state tracking machine, detected and mitigated the attack by identifying out-of-state ACK packets. This highlights the challenge of stateful TCP attacks in asymmetric routing topologies and the necessity of custom software solutions like flowtrackd for effective mitigation.