Pierluigi Paganini
June 20, 2025
Cloudflare blocked a record 7.3 Tbps DDoS attack in May 2025, 12% greater than its previous peak and 1 Tbps greater than the attack reported by the popular cyber journalist Brian Krebs.
The attack targeted a Cloudflare customer, a hosting provider using the company’s DDoS protection solution Magic Transit. Earlier in 2025, Cloudflare reported over 13.5 million DDoS attacks in January and February alone, mainly aimed at its infrastructure and protected hosting providers.
The 7.3 Tbps DDoS attack blasted 37.4 TB of data in just 45 seconds, like streaming 9,350 HD movies or downloading 9.35 million songs in under a minute. It’s the data equivalent of a year of nonstop HD video or 4,000 years’ worth of daily high-res photos, all crammed into less than a minute.
“37.4 terabytes is not a staggering figure in today’s scales, but blasting 37.4 terabytes in just 45 seconds is.” reads the report published by Cloudflare. “It’s the equivalent to flooding your network with over 9,350 full-length HD movies, or streaming 7,480 hours of high-definition video nonstop (that’s nearly a year of back-to-back binge-watching) in just 45 seconds. “
The attack targeted a single IP, hitting an average of 21,925 ports per second and peaking at 34,517, with source ports similarly distributed.
The 7.3 Tbps DDoS attack was multivector, with 99.996% as UDP floods. The rest included QOTD, Echo, NTP, Mirai, Portmap, and RIPv1 attacks.
The researchers reported that the attack came from 122,145 IPs across 5,433 networks in 161 countries. Nearly half originated from Brazil and Vietnam, with the rest spread globally.
The attack averaged 26,855 unique IPs per second, peaking at 45,097. Most traffic came from 5,433 networks, led by Telefonica Brazil (10.5%) and Viettel (9.8%).
“Our systems successfully blocked this record-breaking 7.3 Tbps DDoS attack fully autonomously without requiring any human intervention, without triggering any alerts, and without causing any incidents.” concludes the report. “This demonstrates the effectiveness of our world-leading DDoS protection systems.”
The previous record attack blocked by Cloudflare reached 5.6 Tbps took place during the week of Halloween 2024.
The attack occurred on October 29, when a Mirai-variant botnet composed of 13,000 IoT devices launched a 5.6 Tbps UDP DDoS attack against a Cloudflare Magic Transit customer, an Internet service provider (ISP) from Eastern Asia.
The record-breaking attack lasted only 80 seconds, and the company pointed out that the detection and mitigation were fully automated without human intervention.
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(SecurityAffairs – hacking, Cloudflare)
