The Largest DDoS Attack in History: Cloudflare Blocks 11.5 Tbps Onslaught
Cloudflare has reported blocking the largest volumetric DDoS attack ever recorded, with traffic peaking at an astonishing 11.5 terabits per second. In such attacks, adversaries overwhelm targets with massive floods of data, saturating network bandwidth or exhausting system resources to the point where legitimate users lose access to services and servers.
According to the company, its defense systems have been operating at full capacity in recent weeks, automatically mitigating hundreds of hyper-volumetric assaults. Among them were peaks of 5.1 billion packets per second and the record-breaking 11.5 Tbps. Initially, Cloudflare’s report suggested that the most powerful attack lasted roughly 35 seconds and originated primarily from Google Cloud infrastructure. However, this statement was later corrected: the traffic actually stemmed from multiple sources, including IoT-based botnets and various cloud providers. Google Cloud representatives were quick to emphasize that their security systems functioned normally and that claims about their infrastructure being the dominant source of attack traffic were inaccurate.
This episode set a new benchmark just two months after the previous record. In June, Cloudflare neutralized a 7.3 Tbps attack against an unnamed hosting provider. Before that, the standing record was 3.8 Tbps and 2 billion packets per second, established in October 2024. Microsoft has faced comparable challenges: in January 2022, its infrastructure mitigated a 3.47 Tbps assault targeting an Azure client in Asia, and in July 2024 another campaign disrupted services across Microsoft 365 and Azure worldwide.
In April, Cloudflare published its quarterly report noting a dramatic escalation in DDoS activity. The company recorded a 198% increase quarter-over-quarter and a 358% year-over-year surge in 2024. Over the year, it documented 21.3 million attacks against customers and an additional 6.6 million against its own infrastructure, the latter carried out during an 18-day multi-layered campaign. Attack techniques included SYN floods, Mirai botnet traffic, SSDP amplification, and more.
The sharpest rise has been observed in network-layer attacks, which surged by 509% year-over-year in early 2025. The new record of 11.5 Tbps underscores how rapidly the scale of DDoS threats is intensifying—and how their mitigation demands ever more expansive, automated, and resilient defense systems.
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