What Are the Most Infamous Botnet Attacks in History?

Table of Contents

• What Is a Botnet?
• The Early History of Botnets
• Mafiaboy Attack (2000)
• EarthLink Spammer (2000)
• MyDoom Worm (2004)
• Storm Botnet (2007)
• Zeus Botnet (2007)
• Conficker (2008)
• Cutwail (2009)
• Mariposa (2010)
• Mirai Botnet (2016)
• Emotet (2014-2021)
• Meris (2021)
• 911 S5 Botnet (2024)
• Recent Attacks in 2025
• The Broader Impacts of Botnet Attacks
• How to Prevent Botnet Infections
• Conclusion
• FAQs

What Is a Botnet?

Before we jump into the attacks, let's clarify what a botnet actually is. A botnet is a network of computers or devices that have been infected with malicious software, allowing a hacker—often called a botmaster—to control them remotely without the owners' knowledge. These infected machines are nicknamed "zombies" because they do the bidder's will, like in a horror movie.

Botnets are built by spreading malware through emails, fake downloads, or exploiting weaknesses in software. Once a device is part of the botnet, it can be used for various crimes, such as sending spam, stealing data, or launching distributed denial-of-service (DDoS) attacks, where the botnet floods a website with traffic to knock it offline.

What makes botnets so powerful is their size and distribution. A single hacker controlling thousands or millions of devices can create chaos on a massive scale. They're hard to stop because the attacks come from everyday users' computers, not a single source. As technology advances, botnets have targeted everything from PCs to smart home devices, making them a persistent threat in our connected world.

The Early History of Botnets

Botnets didn't start as the sophisticated threats we know today. Their roots trace back to the late 1990s and early 2000s, when the internet was still young. Early botnets were often built using Internet Relay Chat (IRC) networks, where hackers could command groups of infected computers to perform simple tasks like flooding chat rooms.

The first notable botnet-like attacks emerged around 2000, as broadband internet became more common. Hackers realized they could harness the power of many machines for bigger impacts, like DDoS attacks or spam. These early efforts were crude compared to modern ones, but they laid the groundwork for the botnet boom in the mid-2000s. Governments and companies were caught off guard, leading to a race to develop better defenses.

As we'll see in the following sections, these initial attacks paved the way for more complex botnets that exploited new technologies and vulnerabilities, turning botnets into a multi-billion-dollar problem for cybersecurity.

Mafiaboy Attack (2000)

One of the first botnet attacks to grab global attention was orchestrated by a 15-year-old Canadian teenager known as Mafiaboy. In February 2000, he used a basic botnet to launch DDoS attacks against major websites, including Yahoo, CNN, Amazon, Dell, and eBay.

The attacks worked by overwhelming the sites with fake traffic, making them inaccessible for hours. Yahoo was down for three hours, costing an estimated $1.2 billion in lost revenue across all affected sites. Mafiaboy's botnet wasn't huge by today's standards—perhaps a few hundred machines—but it proved how vulnerable the internet was.

This incident was a wake-up call. It led to Mafiaboy's arrest and highlighted the need for better cybersecurity laws. For beginners, think of it as the digital equivalent of a flash mob blocking a store entrance—simple but effective in causing disruption.

The Mafiaboy attack set the stage for future botnets, showing hackers the power of distributed attacks. It also spurred companies to invest in DDoS protection, though as we'll see, threats only grew more sophisticated.

EarthLink Spammer (2000)

Around the same time as Mafiaboy, the EarthLink Spammer botnet emerged as one of the first focused on email spam. This botnet used compromised computers to send massive amounts of unsolicited emails, promoting scams and products.

Operated by a spammer linked to EarthLink ISP, it infected thousands of machines via phishing emails. The impact was felt in clogged inboxes worldwide, slowing email services and spreading more malware.

While not as flashy as DDoS, spam botnets like this caused economic damage through lost productivity and fraud. Authorities dismantled it, but it showed botnets' versatility beyond just crashing sites.

This attack underscored the profitability of botnets, encouraging cybercriminals to build larger networks for ongoing revenue streams like spam campaigns.

MyDoom Worm (2004)

Moving into the mid-2000s, the MyDoom worm became one of the fastest-spreading botnet creators. Released in January 2004, it infected computers via email attachments, turning them into bots for DDoS and spam.

At its peak, MyDoom infected over a million machines, launching attacks on sites like SCO Group and Microsoft. It caused slowdowns across the internet, with damages estimated at $38 billion.

What made MyDoom infamous was its self-replicating nature—a worm that spread without user interaction after initial infection. It opened backdoors for remote control, making it a true botnet enabler.

This attack highlighted the blend of worms and botnets, a trend that would continue. It also prompted better email security practices, like scanning attachments.

Storm Botnet (2007)

The Storm botnet, also known as Storm Worm, exploded onto the scene in 2007. It infected up to 160,000 computers, using peer-to-peer communication to evade detection.

Spread through emails with subjects like "230 dead as storm batters Europe," it turned machines into spam factories, sending billions of emails daily. Storm was resilient, with bots updating each other without a central server.

Its impact included massive spam waves and DDoS attacks. Researchers struggled to take it down, as shutting one part didn't kill the whole network.

Storm showed botnets' evolution toward decentralization, making them harder to dismantle. It influenced future designs and emphasized the need for advanced threat intelligence.

Zeus Botnet (2007)

Zeus, or Zbot, debuted in 2007 and became notorious for financial theft. With over 3.6 million bots in the US alone, it used keyloggers and form-grabbing to steal banking credentials.

Infecting via drive-by downloads and phishing, Zeus enabled man-in-the-browser attacks, altering web pages to capture data. It led to losses over $100 million.

Law enforcement took down parts in 2010, but variants persist. Zeus highlighted botnets' shift to targeted crime, beyond disruption to direct profit.

This botnet spurred banks to adopt two-factor authentication, changing how we secure online finances.

Conficker (2008)

Conficker, discovered in 2008, grew to over 10.5 million bots, making it one of the largest ever. It exploited Windows vulnerabilities to spread, creating a botnet for spam and DDoS.

With 10 billion spam emails daily capacity, Conficker caused widespread infections, including in governments and hospitals. Its domain generation algorithm made C&C hard to block.

A coalition of experts contained it, but it showed botnets' potential for global disruption. Conficker's legacy is in improved patch management practices.

Cutwail (2009)

Cutwail, active from 2009, was a spam powerhouse with up to 2 million bots. It sent 74 billion spam messages daily, promoting scams and malware.

Spread via trojans, Cutwail's modular design allowed updates. It generated revenue for operators through spam services.

Takedowns occurred, but remnants linger. Cutwail exemplified botnets as businesses, rented to other criminals.

Mariposa (2010)

Mariposa, meaning butterfly, infected millions by 2010. It stole data and launched DDoS, targeting businesses.

An international operation shut it down, arresting operators. Mariposa showed botnets' global reach, affecting Fortune 500 companies.

Its takedown was a win for collaboration between law enforcement and private sector.

Mirai Botnet (2016)

Mirai marked the IoT era in 2016, infecting 380,000 devices like cameras and routers. Using default passwords, it launched record DDoS attacks.

Notable targets: Krebs on Security (620 Gbps), Dyn (disrupting Twitter, Netflix). Source code release led to variants.

Mirai exposed IoT vulnerabilities, prompting better security standards for smart devices.

Emotet (2014-2021)

Emotet started as a banking trojan in 2014, evolving into a botnet for malware delivery. It infected millions, spreading via spam.

Known for resilience, it was taken down in 2021 by global police. Emotet enabled ransomware, causing huge losses.

Its story shows botnets as platforms for other threats.

Meris (2021)

Meris hit in 2021 with 17.2 million RPS DDoS on Yandex. Using compromised routers, it set records.

Impacts included service disruptions, highlighting ongoing DDoS evolution.

911 S5 Botnet (2024)

The 911 S5 was dismantled in 2024, the largest ever with 19 million IPs. Used for fraud, it hid crimes behind residential proxies.

FBI action marked a major victory, but showed botnets' scale.

Recent Attacks in 2025

In 2025, a 5.6 Tbps DDoS hit an Asian ISP, Mirai variant. Cloudflare blocked 7.3 Tbps earlier. These show escalating threats.

The Broader Impacts of Botnet Attacks

Beyond immediate disruption, botnets cause financial losses, privacy breaches, and infrastructure strain. They enable fraud, ransomware, and espionage.

On society, they erode trust in tech. Economically, costs run billions annually.

How to Prevent Botnet Infections

Protect yourself with updates, strong passwords, antivirus. For IoT, change defaults.

• Use firewalls.
• Avoid suspicious emails.
• Monitor network activity.

Businesses: Employ DDoS mitigation, regular scans.

Here's a table summarizing key infamous botnet attacks:

Conclusion

From the early disruptions of Mafiaboy and EarthLink to the massive scales of Mirai and 911 S5, botnet attacks have left an indelible mark on cybersecurity history. We've explored their evolution, key examples, impacts, and prevention tips. These attacks remind us of the internet's vulnerabilities but also of our ability to fight back through awareness and technology. As botnets continue to adapt, staying informed is crucial. Protect your devices, and contribute to a safer online world.

FAQs

What is a botnet?

A botnet is a network of infected devices controlled by hackers to perform malicious tasks like DDoS attacks or spam.

How do botnets form?

Botnets form by infecting devices with malware through emails, downloads, or vulnerabilities, then linking them under remote control.

What was the first major botnet attack?

The Mafiaboy attack in 2000, which used a botnet for DDoS on sites like Yahoo and CNN.

Why are botnets dangerous?

They can disrupt services, steal data, spread spam, and cause financial losses on a large scale.

What is the largest botnet in history?

The 911 S5 botnet, with 19 million IP addresses, dismantled in 2024.

How did the Mirai botnet work?

Mirai infected IoT devices with weak passwords to launch massive DDoS attacks.

What impact did the Storm botnet have?

It sent billions of spam emails and was hard to dismantle due to its peer-to-peer structure.

Was Zeus a botnet?

Yes, Zeus was a botnet focused on stealing financial credentials, infecting millions.

What made Conficker unique?

Its massive size of over 10 million bots and ability to generate random domains for control.

How can I tell if my device is in a botnet?

Signs include slow performance, high data usage, or unexpected crashes; scan with antivirus.

What is a DDoS attack?

A DDoS attack floods a target with traffic to make it unavailable, often using botnets.

Has any botnet been completely eradicated?

Some like Emotet were taken down, but variants often reemerge.

What role do IoT devices play in botnets?

IoT devices are easy targets due to poor security, powering botnets like Mirai.

How do hackers profit from botnets?

Through spam, data theft, ransomware, or renting the botnet to others.

What was the Meris botnet known for?

Record-breaking DDoS attacks with millions of requests per second in 2021.

Can antivirus stop botnets?

Yes, good antivirus can detect and remove botnet malware, but prevention is key.

What laws address botnet attacks?

Laws like the Computer Fraud and Abuse Act in the US prosecute botnet operators.

How have botnets evolved?

From simple IRC-based to decentralized, IoT-focused networks with AI evasion.

What should businesses do against botnets?

Implement firewalls, updates, monitoring, and DDoS mitigation services.

Are there recent botnet attacks in 2025?

Yes, including a 5.6 Tbps DDoS using a Mirai variant.