The 5 most famous DDoS attacks in history

4 min read

By Adrian Taylor

Distributed Denial of Service (DDoS) attacks are now everyday occurrences. Whether you’re a small non-profit or a huge multinational conglomerate, your online services—email, websites, anything that faces the internet—can be slowed or completely stopped by a DDoS attack. Moreover, DDoS attacks are sometimes used to distract your cybersecurity operations while other criminal activity, such as data theft or network infiltration, is underway. 

 DDoS attacks are getting bigger and more frequent 

The first known Distributed Denial of Service attack occurred in 1996 when Panix, now one of the oldest internet service providers, was knocked offline for several days by a SYN flood, a technique that has become a classic DDoS attack. Over the next few years DDoS attacks became common and Cisco predicts that the total number of DDoS attacks will double from the 7.9 million seen in 2018 to something over 15 million by 2023. 

But it’s not just the number of DDoS attacks that are increasing; as the bad guys are creating ever bigger botnets—the term for the armies of hacked devices that are used to generate DDoS traffic—the scale of DDoS attacks is also increasing. A Distributed Denial of Service attack of one gigabit per second is enough to knock most organizations off the internet but we’re now seeing peak attack sizes in excess of one terabit per second generated by hundreds of thousands, or even millions, of suborned devices. Given that IT services downtime costs companies anywhere from $300,000 to over $1,000,000 per hour, you can see that the financial hit from even a short DDoS attack could seriously damage your bottom line.  

So we’re going to take a look at some of the most notable DDoS attacks to date. Our choices include some DDoS attacks that are famous for their sheer scale while others are because of their impact and consequences. 

The AWS DDoS attack in 2020

Amazon Web Services, the 800-pound gorilla of everything cloud computing, was hit by a gigantic DDoS attack in February 2020. This was the most extreme DDoS attack in recent history and it targeted an unidentified AWS customer using a technique called Connectionless Lightweight Directory Access Protocol (CLDAP) Reflection. This technique relies on vulnerable third-party CLDAP servers and amplifies the amount of data sent to the victim’s IP address by 56 to 70 times. The attack lasted for three days and peaked at an astounding 2.3 terabytes per second. While the disruption caused by the AWS DDoS Attack was far less severe than it could have been, the sheer scale of the attack and the implications for AWS hosting customers potentially losing revenue and suffering brand damage are significant. 

The MiraiKrebs and OVH DDoS attacks in 2016 

On September 20, 2016, the blog of cybersecurity expert Brian Krebs was assaulted by a DDoS attack in excess of 620 Gbps, which at the time, was the largest attack ever seen. Krebs had recorded 269 DDoS attacks since July 2012, but this attack was almost three times bigger than anything his site or, for that matter, the internet had seen before.  

The source of the attack was the Mirai botnet, which, at its peak later that year, consisted of more than 600,000 compromised Internet of Things (IoT) devices such as IP cameras, home routers, and video players. Mirai had been discovered in August that same year but the attack on Krebs’ blog was its first big outing. 

The next Mirai attack on September 19 targeted one of the largest European hosting providers, OVH, which hosts roughly 18 million applications for over one million clients. This attack was on a single undisclosed OVH customer and driven by an estimated 145,000 bots, generating a traffic load of up to 1.1 terabits per second, and lasted about seven days. The Mirai botnet was a significant step up in how powerful a DDoS attack could be. The size and sophistication of the Mirai network was unprecedented, as was the scale of the attacks and their focus. 

The MiraiDyn DDoS attack in 2016 

Before we discuss the third notable Mirai DDoS attack of 2016, there’s one related event that should be mentioned: On September 30, someone claiming to be the author of the Mirai software released the source code on various hacker forums and the Mirai DDoS platform has been replicated and mutated scores of times since. 

On October 21, 2016, Dyn, a major Domain Name Service (DNS) provider, was assaulted by a one-terabit-per-second traffic flood that then became the new record for a DDoS attack. There’s some evidence that the DDoS attack may have actually achieved a rate of 1.5 terabits per second. The traffic tsunami knocked Dyn’s services offline rendering a number of high-profile websites including GitHub, HBO, Twitter, Reddit, PayPal, Netflix, and Airbnb, inaccessible. Kyle York, Dyn’s chief strategy officer, reported, “We observed 10s of millions of discrete IP addresses associated with the Mirai botnet that were part of the attack.” 

Mirai supports complex, multi-vector attacks that make mitigation difficult. Even though Mirai was responsible for the biggest assaults up to that time, the most notable thing about the 2016 Mirai attacks was the release of the Mirai source code enabling anyone with modest information technology skills to create a botnet and mount a Distributed Denial of Service attack without much effort.

The six banks DDoS attack in 2012

On March 12, 2012, six U.S. banks were targeted by a wave of DDoS attacks—Bank of America, JPMorgan Chase, U.S. Bank, Citigroup, Wells Fargo, and PNC Bank. The attacks were carried out by hundreds of hijacked servers from a botnet called Brobot, with each attack generating over 60 gigabits of DDoS attack traffic per second. 

At the time, these attacks were unique in their persistence: Rather than trying to execute one attack and then backing down, the perpetrators barraged their targets with a multitude of attack methods in order to find one that worked. So, even if a bank was equipped to deal with a few types of DDoS attacks, they were helpless against other types of attack. 

The most remarkable aspect of the bank attacks in 2012 was that the attacks were allegedly carried out by the Izz ad-Din al-Qassam Brigades, the military wing of the Palestinian Hamas organization. Moreover, the attacks had a huge impact on the affected banks in terms of revenue, mitigation expenses, customer service issues, and the banks’ branding and image. 

The GitHub attack in 2018

On Feb. 28, 2018, GitHub—a platform for software developers—was hit with a DDoS attack that clocked in at 1.35 terabits per second and lasted for roughly 20 minutes. According to GitHub, the traffic was traced back to “over a thousand different autonomous systems (ASNs) across tens of thousands of unique endpoints.” 

Even though GitHub was well prepared for a DDoS attack their defenses were overwhelmed—they simply had no way of knowing that an attack of this scale would be launched.  

The GitHub DDoS attack was notable for its scale and the fact that the attack was staged by exploiting a standard command of Memcached, a database caching system for speeding up websites and networks. The Memcached DDoS attack technique is particularly effective as it provides an amplification factor—the ratio of the attacker’s request size to the amount of DDoS attack traffic generated—of up to a staggering 51,200 times. 

And that concludes our top five line up. It is a sobering insight into just how powerful, persistent and disruptive DDoS attacks have become.

About the author

Adrian Taylor is the Regional VP of Sales for A10 Networks. A10 employs advanced defense strategies that protect against all kinds of cyberattacks including new, novel DDoS attacks. Download their latest report The State of DDoS Weapons

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