Huayi Duan, Marco Bearzi, Jodok Vieli, David Basin, Adrian Perrig, and Si Liu, ETH Zürich; Bernhard Tellenbach, Armasuisse

While DNS is often exploited by reflective DoS attacks, it can also be weaponized as a powerful amplifier to overload itself, as evidenced by a stream of recently discovered application-layer amplification attacks. Given the importance of DNS, the question arises of what the fundamental traits are for such attacks. To answer this question, we perform a systematic investigation by establishing a taxonomy of amplification primitives intrinsic to DNS and a framework to analyze their composability. This approach leads to the discovery of a large family of compositional amplification (CAMP) vulnerabilities, which can produce multiplicative effects with message amplification factors of hundreds to thousands. Our measurements with popular DNS implementations and open resolvers indicate the ubiquity and severity of CAMP vulnerabilities and the serious threats they pose to the Internet's crucial naming infrastructure.