Cloudflare Thwarts Record-Breaking 7.3 Tbps DDoS Attack: Tips to Protect Your Network

Cloudflare, a renowned content delivery network (CDN) and security provider, recently thwarted the largest Distributed Denial of Service (DDoS) attack in internet history. The attack, which targeted an unnamed hosting provider using Cloudflare’s Magic Transit DDoS protection service, peaked at a staggering 7.3 terabits per second (Tbps) and delivered 37.4 terabytes of data in just 45 seconds. This data deluge, equivalent to streaming nearly 10,000 high-definition movies in under a minute, was primarily constituted by User Datagram Protocol (UDP) flood attacks, known for their high data transmission speeds. UDP floods target high volumes of traffic to overwhelm network resources. This particular attack was highly distributed, originating from 122,145 source IP addresses across 161 countries, with Brazil, Vietnam, Taiwan, China, Indonesia, and Ukraine contributing the majority of the malicious traffic. The attack bombarded an average of 21,925 destination ports per second, reaching a peak of 34,517 ports per second on a single IP address. Cloudflare’s successful mitigation of this record-breaking attack comes at a time when DDoS incidents are surging. In the first quarter of 2025, Cloudflare mitigated 20.5 million DDoS attacks, marking a 358% year-over-year increase and nearly matching the total for all of 2024. Most of these attacks were network-layer assaults leveraging UDP floods, with the company blocking around 700 hyper-volumetric attacks—those exceeding 1 Tbps—averaging eight per day. Earlier in 2025, Cloudflare also defended against a 6.5 Tbps attack attributed to the Eleven11bot botnet, which leveraged tens of thousands of compromised webcams and video recorders. Global trends indicate a sharp rise in DDoS attacks. Radware, a cloud security company, reported an 800% surge in hacktivist DDoS attack claims against the United States following the Israel-Iran conflict between June 21-22, 2025. Radware’s 2025 Global Threat Analysis Report highlighted a 550% increase in web DDoS attacks globally and a nearly 400% year-over-year growth in DDoS attack volume. To protect against such threats, businesses and organizations can implement several strategies: Partner with DDoS Mitigation Providers: Engage services from reputable firms like Akamai, Cloudflare, Imperva, or Radware. These companies have the expertise and infrastructure to handle large-scale attacks effectively. Block Traffic from Known Bad ASNs: Filter out traffic from sources with a history of abuse, although this method is not foolproof as savvy attackers can use IP spoofing or botnets on wireless routers, DVRs, and webcams to circumvent geoblocking. Distributed Network Infrastructure: Spread out network resources to avoid single points of failure and reduce vulnerability to DDoS attacks. Router and Firewall Configuration: Configure routers and firewalls to drop junk packets and block unsafe protocols like ICMP, FTP, and telnet at the network edge. Invest in robust firewalls and intrusion prevention systems (IPS) capable of handling large traffic volumes without performance degradation. Upstream ISP Cooperation: Work with your Internet Service Provider (ISP) to block unnecessary or unwanted upstream traffic. For instance, if you don’t need UDP traffic, ensure it is blocked at the ISP level. Web Application Firewalls (WAFs): Use WAFs to defend against Layer 7 application attacks, which target web applications with malicious traffic. Multiple DNS Providers and DNSSEC: Employ more than one DNS provider and secure your domain with DNSSEC to maintain site availability even if one provider is compromised. Specific Software Defenses: Utilize specialized applications like Wordfence for platforms such as WordPress to enhance security. Layered Defenses: Implement multiple, overlapping security measures to ensure comprehensive protection. No single defense can reliably withstand all types of attacks. Red Team Testing: Proactively test your defenses by simulating attacks using tools like GoldenEye, hping3, and HULK to identify and rectify vulnerabilities. Even small businesses and websites are not immune to DDoS attacks. For instance, the author of this piece runs a modest site, Practical Technology, and regularly faces an average of a dozen DDoS attacks per week. In the increasingly hostile digital landscape, maintaining robust DDoS defenses is crucial for ensuring continued online presence and operational integrity. Industry insiders emphasize that the growing sophistication and frequency of DDoS attacks necessitate advanced and multi-layered defense mechanisms. Cloudflare’s capabilities in mitigating such attacks highlight its position as a leader in cybersecurity. However, the rapid escalation in attack intensity underscores the need for continuous improvement and adaptation in security strategies to stay ahead of evolving threats.