Motivated by the impressive but diffuse scope of DDoS research and reporting, we undertake a multistakeholder (joint industry-academic) analysis to seek convergence across the best available macroscopic views of the relative trends in two dominant classes of attacks - direct-path attacks and reflection-amplification attacks. We first analyze 24 industry reports to extract trends and (in)consistencies across observations by commercial stakeholders in 2022. We then analyze ten data sets spanning industry and academic sources, across four years (2019-2023), to find and explain discrepancies based on data sources, vantage points, methods, and parameters. Our method includes a new approach: we share an aggregated list of DDoS targets with industry players who return the results of joining this list with their proprietary data sources to reveal gaps in visibility of the academic data sources. We use academic data sources to explore an industry-reported relative drop in spoofed reflection-amplification attacks in 2021-2022. Our study illustrates the value, but also the challenge, in independent validation of security-related properties of Internet infrastructure. Finally, we reflect on opportunities to facilitate greater common understanding of the DDoS landscape. We hope our results inform not only future academic and industry pursuits but also emerging policy efforts to reduce systemic Internet security vulnerabilities.

In this paper, we present a detailed performance analysis of QUIC instant~ACK, a standard-compliant approach to reduce waiting times during the QUIC connection setup in common CDN deployments. To understand the root causes of the performance properties, we combine numerical analysis and the emulation of eight QUIC implementations using the QUIC Interop Runner. Our experiments comprehensively cover packet loss and non-loss scenarios, different round trip times, and TLS certificate sizes. To clarify instant ACK deployments in the wild, we conduct active measurements of 1M~popular domain names. For almost all domain names under control of Cloudflare, Cloudflare uses instant ACK, which in fact improves performance. We also find, however, that instant ACK may lead to unnecessary retransmissions or longer waiting times under some network conditions, raising awareness of drawbacks of instant ACK in the future.

On December 10, 2021, Log4Shell was disclosed to the public and was quickly recognized as a most severe vulnerability. It exploits a bug in the wide-spread Log4j library that allows for critical remote-code-execution (RCE). Any service that uses this library and exposes an interface to the Internet is potentially vulnerable. In this paper, we report about a measurement study starting with the day of disclosure. We follow the rush of scanners during the first two months after the disclosure and observe the development of the Log4Shell scans in the subsequent year. Based on traffic data collected at several vantage points we analyze the payloads sent by researchers and attackers. We find that the initial rush of scanners ebbed quickly, but continued in waves throughout 2022. Benign scanners showed interest only in the first days after the disclosure, whereas malicious scanners continue to target the vulnerability. During both periods, a single entity appears responsible for the majority of the malicious activities.

In this paper, we revisit the use of honeypots for detecting reflective amplification attacks. These measurement tools require careful design of both data collection and data analysis including cautious threshold inference. We survey common amplification honeypot platforms as well as the underlying methods to infer attack detection thresholds and to extract knowledge from the data. By systematically exploring the threshold space, we find most honeypot platforms produce comparable results despite their different configurations. Moreover, by applying data from a large-scale honeypot deployment, network telescopes, and a real-world baseline obtained from a leading DDoS mitigation provider, we question the fundamental assumption of honeypot research that convergence of observations can imply their completeness. Conclusively we derive guidance on precise, reproducible honeypot research, and present open challenges.

In this paper, we revisit the performance of the QUIC connection setup and relate the design choices for fast and secure connections to common Web deployments. We analyze over 1M Web domains with 272k QUIC-enabled services and find two worrying results. First, current practices of creating, providing, and fetching Web certificates undermine reduced round trip times during the connection setup since sizes of 35% of server certificates exceed the amplification limit. Second, non-standard server implementations lead to larger amplification factors than QUIC permits, which increase even further in IP spoofing scenarios. We present guidance for all involved stakeholders to improve the situation.

In this paper, we present first measurements of Internet background radiation originating from the emerging transport protocol QUIC. Our analysis is based on the UCSD network telescope, correlated with active measurements. We find that research projects dominate the QUIC scanning ecosystem but also discover traffic from non-benign sources. We argue that although QUIC has been carefully designed to restrict reflective amplification attacks, the QUIC handshake is prone to resource exhaustion attacks, similar to TCP SYN floods. We confirm this conjecture by showing how this attack vector is already exploited in multi-vector attacks: On average, the Internet is exposed to four QUIC floods per hour and half of these attacks occur concurrently with other common attack types such as TCP/ICMP floods.