PCMag editors select and review products independently. If you buy through affiliate links, we may earn commissions, which help support our testing.

Microsoft Fends Off 2.4Tbps DDoS Attack, Second Largest on Record

The attack targeted an Azure customer and originated from '70,000 sources' based in countries across Asia and the US, Microsoft says.

 & Michael Kan Principal Reporter

Our team tests, rates, and reviews more than 1,500 products each year to help you make better buying decisions and get more from technology.

Our Expert
LOOK INSIDE PC LABS HOW WE TEST
65 EXPERTS
43 YEARS
41,500+ REVIEWS

A hacker tried to take down a Microsoft customer’s internet services with the second largest DDoS attack on record this past August.  

On Monday, the company reported it encountered the 2.4Tbps attack targeting a Microsoft Azure customer based in Europe. The current record holder is a 2.5 Tbps assault Google fended off back in 2017.

A DDoS attack essentially tries to down a website or internet service by bombarding the system with a flood of data traffic. To do so, the hacker can sometimes harness botnets, or armies of malware-infected computers, to generate the traffic. 

In this case, the attack originated from “70,000 sources” based in countries across Asia and the US, Microsoft says. Whether the hacker used a botnet was left unsaid. But the UDP protocol was exploited in what’s known as a “reflection attack” to amplify the data traffic to 2.4Tbps. 

The DDoS attack measured over time.

According to Microsoft, the attack lasted for only 10 minutes and occured in waves. “In total, we monitored three main peaks, the first at 2.4 Tbps, the second at 0.55 Tbps, and the third at 1.7 Tbps,” Microsoft added. 

The attack would’ve been enough to disrupt a company running their own data center. However, Microsoft says it successfully mitigated the attack, thanks to Azure’s DDoS protection service, which is capable of absorbing “tens of terabits of DDoS attacks.”

“This aggregated distributed mitigation capacity can massively scale to absorb the highest volume of DDoS threats, providing our customers the protection they need,” Microsoft adds. 

The August attack edges out the 2.3Tbps DDoS incident Amazon experienced in 2020; a hacker exploited hijacked Connection-Less Lightweight Directory Access Protocol (CLDAP) servers to send a flood of traffic to an Amazon AWS customer. However, like Microsoft, Amazon was able to mitigate the assault. 

The incidents show that the biggest internet providers can fend off even the mightiest DDoS attacks. Hence, the companies have been using their DDoS protection capabilities to also market their cloud internet services. 

In August and September, Cloudflare and Russian internet company Yandex also encountered two massive DDoS attacks. But the assaults occurred over a separate attack vector that exploited HTTP browser-based requests, so the incidents were measured differently.

The incident that hit Cloudflare reached 17.2 million requests per second while the assault on Yandex peaked at nearly 22 million rps. However, both companies say they repelled the attacks.

About Our Expert

Michael Kan

Michael Kan

Principal Reporter

My Experience

I've been a journalist for over 15 years. I got my start as a schools and cities reporter in Kansas City and joined PCMag in 2017, where I cover satellite internet services, cybersecurity, PC hardware, and more. I'm currently based in San Francisco, but previously spent over five years in China, covering the country's technology sector.

Since 2020, I've covered the launch and explosive growth of SpaceX's Starlink satellite internet service, writing 600+ stories on availability and feature launches, but also the regulatory battles over the expansion of satellite constellations, fights with rival providers like AST SpaceMobile and Amazon, and the effort to expand into satellite-based mobile service. I've combed through FCC filings for the latest news and driven to remote corners of California to test Starlink's cellular service.

I also cover cyber threats, from ransomware gangs to the emergence of AI-based malware. In 2024 and 2025, the FTC forced Avast to pay consumers $16.5 million for secretly harvesting and selling their personal information to third-party clients, as revealed in my joint investigation with Motherboard.

I also cover the PC graphics card market. Pandemic-era shortages led me to camp out in front of a Best Buy to get an RTX 3000. I'm now following how the AI-driven memory shortage is impacting the entire consumer electronics market. I'm always eager to learn more, so please jump in the comments with feedback and send me tips.

The Best Tech I've Had:

  • My first video game console: a Nintendo Famicom
  • I loved my Sega Saturn despite PlayStation's popularity.
  • The iPod Video I received as a gift in college
  • Xbox 360 FTW
  • The Galaxy Nexus was the first smartphone I was proud to own.
  • The PC desktop I built in 2013, which still works to this day.

Read full bio