CloudFlare Infrastructure Hit With 400Gbs NTP-Based DDoS Attack

Web performance and security firm CloudFlare said late Monday that a customer running on its platform was hit with a massive DDoS attack today that affected service in much of Europe and then into some of its US infrastructure.

“It was a very large DDoS targeting a CloudFlare customer,” Matthew Prince, CEO of Cloudflare told SecurityWeek. “We’re still gathering the log data to get exact numbers but know it was well over 300Gbps and likely over 400Gbps,” Prince said.

“The method was NTP reflection, which is quickly replacing DNS reflection as the source of the largest attacks,” Prince said. 

NTP stands for Network Time Protocol, which runs over port 123 and is used to synchronize clocks between machines on a network. In December, researchers at Symantec noticed an uptick of attacks targeting the protocol.

“NTP is effective as an amplification source because the responses can be hundreds of times the size of the queries,” Prince explained. “This means that an attacker with a list of a relatively small number of vulnerable NTP servers can generate a large attack. Generally, you only need about 1/10th the number of misconfigured NTP servers as you do open DNS resolvers to launch an attack of the same size.”

US-CERT warned about these types of distributed denial-of-service attacks earlier this year. 

“We were able to largely mitigate the attack across our global network,” Prince added. “We did see congestion in Europe that caused some slowness in the region. We’re continuing to add capacity worldwide to stay ahead of ever larger attacks we’re seeing.”

CloudFlare did not name the customer that was targeted in this particular attack. 

CloudFlare, which is usually quite transparent about its operations, will likely share more details as the attack is analyzed and mitigated.