The Biggest Cyber Attacks in History & How They Happened

The First Major Internet Attack

While primitive by today’s standards, the Morris Worm holds the distinction of being the first major internet attack and a wake-up call about the vulnerabilities inherent in networked systems.

How it happened: Created by Robert Tappan Morris, then a graduate student at Cornell University, the worm was released on November 2, 1988. Morris claimed he designed it not as a destructive tool but as a way to gauge the size of the internet. However, a programming error caused it to replicate much faster than intended.

The worm exploited vulnerabilities in Unix sendmail, finger, and rsh/rexec, along with weak password security. It would check if a system was already infected, but a critical flaw in this verification mechanism allowed multiple infections of the same machine, eventually overwhelming system resources.

Impact: The worm infected approximately 10% of all internet-connected computers (about 6,000 machines) and caused between $100,000-$10 million in damages. More significantly, it led to the formation of the first Computer Emergency Response Team (CERT) and sparked a new era of cybersecurity awareness.

Early State-Sponsored Cyber Espionage

Titan Rain represents one of the first documented cases of large-scale, coordinated cyber espionage likely conducted by a nation-state actor.

How it happened: The attack series, attributed by many experts to hackers supported by the Chinese government (though this was never officially confirmed), targeted U.S. defense contractors, military installations, government agencies, and aerospace companies.

The attackers used a combination of spear-phishing emails, zero-day exploits, and sophisticated trojans to gain access to sensitive systems. Once inside, they methodically extracted large amounts of data, often operating during U.S. nighttime hours to reduce the chance of detection.

Impact: While the full extent remains classified, Titan Rain is believed to have resulted in the theft of hundreds of terabytes of sensitive data, including information on military systems like the Space Shuttle, the F-35 Joint Strike Fighter, and various defense planning documents.

The First Digital War

Often described as the first instance of cyber warfare, the 2007 attacks against Estonia demonstrated how digital attacks could effectively target an entire nation.

How it happened: Following Estonia’s decision to relocate a Soviet-era war memorial, the country experienced an unprecedented series of cyber attacks. The operation began with simple ping floods and escalated to sophisticated botnet-driven distributed denial-of-service (DDoS) attacks targeting government websites, online banking services, and media outlets.

The attacks were coordinated through Russian-language forums, where detailed instructions were shared on how to conduct DDoS attacks. While Russia was widely suspected to be behind the attacks, definitive attribution was never established.

Impact: For nearly three weeks, Estonia’s digital infrastructure was severely compromised. Bank cards and online banking services were unavailable for days, government communications were disrupted, and media outlets couldn’t publish news online. The attack fundamentally changed how nations approach cybersecurity, leading directly to the establishment of NATO’s Cooperative Cyber Defence Centre of Excellence in Tallinn.

The World’s First Digital Weapon

Stuxnet marked a watershed moment in cyber warfare as the first malware specifically designed to target physical infrastructure, demonstrating that digital attacks could cause real-world physical damage.

How it happened: Believed to be created by U.S. and Israeli intelligence agencies (though never officially acknowledged), Stuxnet was a highly sophisticated worm targeting Iran’s uranium enrichment facilities. What made it revolutionary was its precise targeting of Siemens industrial control systems (ICS) and programmable logic controllers (PLCs).

The malware spread via USB drives and network shares, exploiting four zero-day vulnerabilities. Once inside the target network, it searched specifically for Siemens Step7 software used to program industrial control systems. When it found its target—the centrifuges at Iran’s Natanz facility—it altered the rotation speeds, causing physical damage while simultaneously feeding false readings to monitoring systems to hide the attack.

Impact: Stuxnet reportedly destroyed nearly 1,000 uranium enrichment centrifuges, setting back Iran’s nuclear program by years. Beyond the physical damage, Stuxnet forever changed the threat landscape by demonstrating that critical infrastructure was vulnerable to cyber attacks. Its legacy lives on in the subsequent development of industrial control system security protocols and in the proliferation of ICS-targeting malware that followed.

Hollywood’s Digital Nightmare

The Sony Pictures hack represents one of the most destructive cyber attacks against a private corporation and highlighted how vulnerable even major companies were to determined attackers.

How it happened: A group calling themselves “Guardians of Peace” (GOP) infiltrated Sony Pictures’ network, likely using spear-phishing emails that gave them initial access. Once inside, they spent weeks mapping the network and exfiltrating data before deploying destructive malware.

On November 24, 2014, employees found their computers locked with a menacing image of a skeleton and the GOP logo. The attackers used a wiper malware called WhiskeyAlfa that overwrote the master boot record of infected computers and deleted files, making recovery nearly impossible.

The attack was attributed to North Korea, likely in retaliation for Sony’s planned release of “The Interview,” a comedy depicting the assassination of North Korean leader Kim Jong-un.

Impact: The breach resulted in the leak of confidential data including unreleased films, personal employee information, executive emails, salary details, and copies of passports and visas. Sony estimated the direct cost of the attack at $35 million, but the reputational damage was incalculable. The incident also raised concerns about nation-states targeting private companies for political reasons.

The Global Ransomware Pandemic

WannaCry represented a perfect storm of ransomware tactics, sophisticated exploits, and rapid propagation methods that created one of the most widespread and costly cyber attacks in history.

How it happened: On May 12, 2017, WannaCry began infecting computers globally. What made it uniquely dangerous was its worm-like capability to self-propagate across networks. It exploited a Windows vulnerability called EternalBlue, which had been stolen from the NSA and leaked by a group called the Shadow Brokers just a month earlier.

Microsoft had released a patch for the vulnerability in March 2017, but many organizations hadn’t applied it. Once WannaCry infected a system, it encrypted files and demanded a Bitcoin ransom of $300-$600 for decryption. It infected new targets by scanning for vulnerable SMB ports (445) on other networked computers.

The attack was attributed to the Lazarus Group, linked to North Korea.

Impact: Within just 24 hours, WannaCry had infected more than 230,000 computers across 150 countries. Notable victims included the UK’s National Health Service (NHS), where thousands of appointments and surgeries had to be canceled, Spanish telecommunications company Telefónica, FedEx, and numerous other organizations worldwide. The estimated damages exceeded $4 billion globally.

The Most Sophisticated Supply Chain Attack

The SolarWinds breach represented an unprecedented level of sophistication in supply chain attacks and demonstrated how trusted software update mechanisms could be weaponized.

How it happened: Suspected Russian intelligence operatives (APT29, also known as Cozy Bear) compromised the software development environment of SolarWinds, a major IT management company. The attackers inserted malicious code into the company’s Orion software updates, which were then automatically distributed to thousands of customers.

The malware, dubbed SUNBURST, remained dormant for up to two weeks after installation to avoid detection. It then established communication with command-and-control servers, allowing attackers to handpick high-value targets for further exploitation. The attackers went to extraordinary lengths to ensure stealth, including using IP addresses from the same country as the victim and carefully timing their activities to match the target’s working hours.

Impact: Over 18,000 organizations received the compromised updates, including numerous U.S. government agencies like the Treasury, Justice, Energy, and Commerce Departments, as well as major corporations like Microsoft, Cisco, and Intel. The attackers gained access to some of the most sensitive government networks for at least nine months before discovery. The full extent of data theft remains unknown, but the breach is considered one of the most significant intelligence coups in modern history.

When Cyber Attacks Met Critical Infrastructure

The Colonial Pipeline attack demonstrated how ransomware could have far-reaching consequences beyond data loss, affecting critical physical infrastructure and causing widespread disruption to everyday life.

How it happened: On May 7, 2021, Colonial Pipeline, which operates the largest petroleum pipeline in the United States, suffered a ransomware attack by the cybercriminal group DarkSide. The hackers gained entry through a legacy VPN account that wasn’t protected with multi-factor authentication.

After infiltrating Colonial’s IT network, the attackers deployed ransomware that encrypted critical billing systems. Although the operational technology (OT) networks that directly control the pipeline were not compromised, Colonial had to shut down the pipeline as a precautionary measure because they couldn’t bill customers or monitor fuel deliveries.

Impact: The 5,500-mile pipeline, which supplies 45% of the East Coast’s fuel, remained offline for six days. This led to widespread panic buying, fuel shortages across multiple states, and spikes in gas prices. Colonial paid a ransom of 75 Bitcoin (approximately $4.4 million at the time), though a portion was later recovered by the FBI. The attack prompted President Biden to sign an executive order to improve the nation’s cybersecurity and led to new mandatory reporting requirements for critical infrastructure companies.

The Internet’s Most Dangerous Vulnerability

The Log4j vulnerability (CVE-2021-44228, also known as Log4Shell) represented one of the most severe security flaws ever discovered, with its impact continuing to reverberate through the digital landscape.

How it happened: In December 2021, security researchers discovered a critical zero-day vulnerability in Log4j, a ubiquitous Java logging library used by millions of applications worldwide. The flaw allowed attackers to execute arbitrary code on vulnerable servers through a relatively simple JNDI lookup string.

What made Log4Shell particularly dangerous was its ease of exploitation combined with Log4j’s widespread use across everything from enterprise applications to cloud services and even devices in the Internet of Things (IoT) ecosystem. Within hours of public disclosure, hackers worldwide began scanning for vulnerable systems.

Multiple threat actors exploited the vulnerability, deploying everything from cryptominers to ransomware. Nation-state actors from China, Iran, North Korea, and Turkey were observed leveraging Log4Shell in their operations.

Impact: The full impact is difficult to quantify due to the vulnerability’s pervasive nature. Major companies affected included Amazon, Apple, Cisco, Google, IBM, Microsoft, and countless others. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) director called it “one of the most serious vulnerabilities” she had seen in her entire career. Even in 2023, organizations continue to discover and patch Log4j vulnerabilities in their systems.