A new record was set for cyberattacks in May 2025 when Cloudflare blocked a distributed denial-of-service (DDoS) attack that peaked at 7.3 terabits per second, the largest ever seen. The attack targeted an unnamed hosting provider and delivered 37.4 terabytes of data in just 45 seconds, enough to stream more than 9,300 HD movies or nearly a year’s worth of high-definition video in under a minute.
How the Attack Unfolded
The attackers used a “carpet bombing” strategy, flooding an average of 22,000 destination ports on a single IP address, with a peak of 34,500 ports per second. The majority of the traffic consisted of UDP packets, which are often used in real-time applications like video streaming and online gaming because they transmit data quickly without checking for delivery. The attack originated from over 122,000 unique IP addresses across 161 countries, with significant traffic coming from Brazil, Vietnam, Taiwan, China, Indonesia, and Ukraine.
Cloudflare’s Magic Transit system, designed to protect network infrastructure from large-scale attacks, automatically detected and mitigated the threat before it could disrupt the targeted service5. The scale and speed of this attack highlight the growing power and sophistication of DDoS threats facing critical internet infrastructure today.
