Cloudflare Holds Back the Tide on 11.5Tbps DDoS Attack

Cloudflare has been mitigating hundreds of DDoS attacks, with one peak reaching 11.5 Tbps in a 35-second UDP flood that drew traffic from multiple IoT and cloud providers, including Google Cloud as a data source and others not disclosed. According to Cloudflare, over the past weeks it autonomously blocked hundreds of hyper-volumetric DDoS attacks, the largest of which reached 5.1 Bpps and 11.5 Tbps.

Researchers at Akamai note that volumetric attacks account for around 75% of DDoS incidents, and industry experts emphasise that the impact of an attack is not solely the size but the combination of volume with persistence or complexity. In June, Cloudflare reported a 7.3 Tbps attack delivering 37.4 terabytes in 45 seconds, following mid‑May events that reached 6.5 Tbps and 4.8 billion pps, which were described by Omer Yoachimik of Cloudflare as a demonstration of effects beyond raw bandwidth.

RETN researchers caution that the peak size matters less than the overall complexity and user experience during an attack. Cloudflare says it plans to release a report with further details. September 3, 2025.