Amplification DDoS attacks remain a prevalent and severe threat to the Internet, with recent attacks reaching the Tbps range. However, all amplification attack vectors known to date were either found by researchers through laborious manual analysis or could only be identified postmortem following large attacks. Ideally, though, an attack vector is discovered and mitigated before the first attack can occur. To this end, we present AMPFUZZ, the first systematic approach to finding amplification vectors in UDP services in a protocol-agnostic way. AMPFUZZ is based on the state-of-the-art greybox fuzzing boosted by a novel technique to make fuzzing UDP-aware, which significantly increases performance. We evaluate AMPFUZZ on 28 Debian network services, where we (re-)discover 7 known and 6 previously unreported amplification vulnerabilities.
USENIX Security Symposium (USENIX Security), 2022.