Azure stops biggest DDoS attack ever, according to Microsoft

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Microsoft Logo (Image credit: Daniel Rubino / Windows Central)

What you need to know

  • Microsoft's Azure DDoS Protection team mitigated an 'unprecedented level' of attacks in the second half of 2021.
  • At one point in 2021, Microsoft stopped an average of 1,955 DDoS attacks per day.
  • Microsoft mitigated an attack with a throughput of 3.47 Tbps in November, which is believed to be the largest attack of its type in history.

Microsoft saw an 'unprecedented level' of Distributed Denial-of-Service (DDoS) attacks in the second half of 2021. The company explains in an Azure blog post that both the complexity and frequency of DDoS attacks reached new levels during that time. In the second half of the year, Microsoft mitigated an average of 1,955 attacks per day. A total of 359,713 unique attacks were stopped by Microsoft in the final six months of 2021.

DDoS attacks essentially spam a website to prevent it from working properly. They are often used by gamers to harm other people's networks to ensure victory. Last year, DDOS attacks targeted Blizzard games, Titanfall, Final Fantasy 14, and several other big-name titles. DDoS attacks can also be used for more malicious purposes, such as shutting down a retail website during the holidays.

A DDoS ransom attack uses the same methods as a traditional DDoS attack, but the malicious actor demands payment in exchange for allowing a site to work again.

Cloudflare has a video explaining and illustrating how DDoS attacks work.

The Microsoft Azure YouTube channel has a video on how to defend against DDoS attacks, though it doesn't have cute animations like Cloudflare's video.

Microsoft mitigated a DDoS attack with a throughput of 3.47 Tbps in November 2021. The company believes it to be the largest DDoS attack in history. The attack involved 10,000 sources from several countries, contributing to an offensive that lasted roughly 15 minutes.

While not quite as large as the November attack, Microsoft also mitigated 2.5 Tbps and 3.25 Tbps DDoS attacks in December 2021.

Microsoft's blog post explains that Azure's DDoS protection platform works by having pipelines that can "scale enormously." This allows the platform to absorb even the largest of DDoS attacks.

Sean Endicott
News Writer and apps editor

Sean Endicott brings nearly a decade of experience covering Microsoft and Windows news to Windows Central. He joined our team in 2017 as an app reviewer and now heads up our day-to-day news coverage. If you have a news tip or an app to review, hit him up at