Cloudflare Blocks Record-Breaking 11.5 Tbps DDoS Attack

On 2 September 2025, SecurityWeek reported that Cloudflare blocked the largest distributed denial-of-service attack ever recorded, at 11.5 Tbps. The attack was a UDP flood that mainly originated from Google Cloud infrastructure and lasted about 35 seconds, according to Cloudflare. Cloudflare noted that over the past weeks it had autonomously blocked hundreds of hyper-volumetric DDoS attacks, with the largest peaks of 5.1 Bpps and 11.5 Tbps.

The 11.5 Tbps incident followed a 7.3 Tbps DDoS attack seen in mid-May, which targeted a hosting provider, lasted 45 seconds, and involved about 37.4 Tb of traffic from over 122,000 IP addresses. Cloudflare’s interception of these assaults is part of a trend of rising DDoS activity: the company mitigated 27.8 million DDoS attacks in the first half of 2025, surpassing the total for all of 2024.

Written by Ionut Arghire for SecurityWeek, the article highlights the ongoing scale of volumetric attacks and Cloudflare’s continued efforts to defend against them.