Exploit Examples (2023): The 11 Worst Attacks of All Time

By Tibor Moes / Updated: May 2023

Exploit Examples (2023): The 11 Worst Attacks of All Time

Computer Exploit Examples

Imagine you’re in a mansion, filled with secret doors and hidden rooms. Now picture a burglar, finding these secret doors and sneaking in to steal your valuables. That’s what happens when a computer system is exploited. The burglar is the hacker, the mansion is your system, and the secret doors are the exploits.

Get ready as we walk you through the most notorious exploit examples ever.


An exploit is a digital break-in tool. It’s a piece of software, chunk of data, or sequence of commands that takes advantage of a bug or vulnerability to cause unintended or unanticipated behavior in computer software, hardware, or something electronic, often for malicious purposes.

  1. Morris Worm (1988): One of the first computer worms distributed via the Internet, it exploited vulnerabilities in Unix sendmail, finger, and rsh/rexec.
  2. Code Red (2001): This worm exploited a buffer overflow vulnerability in Microsoft’s IIS web server.
  3. SQL Slammer (2003): This worm rapidly propagated and caused a denial of service on some Internet hosts by exploiting a buffer overflow in Microsoft’s SQL Server and Desktop Engine database products.
  4. Sasser (2004): Exploiting a vulnerability in Windows’ Local Security Authority Subsystem Service (LSASS), this worm caused infected systems to crash and reboot.
  5. Conficker (2008): Known also as Downup or Downadup, it exploited a vulnerability in Windows OS to create a botnet.
  6. Stuxnet (2010): This worm targeted the programmable logic controllers (PLCs) used in Iran’s nuclear program by exploiting four zero-day vulnerabilities.
  7. Heartbleed (2014): This bug exploited a vulnerability in the OpenSSL cryptographic software library, enabling attackers to steal protected information.
  8. Shellshock (2014): This bug affected Unix-based operating systems, allowing unauthorized users to gain control over affected systems.
  9. Petya/NotPetya (2016/2017): These ransomwares exploited the EternalBlue vulnerability in Microsoft’s implementation of the SMB protocol.
  10. WannaCry (2017): This ransomware worm also used the EternalBlue exploit to spread, affecting systems worldwide.
  11. Meltdown/Spectre (2018): These hardware vulnerabilities affected processors and could allow attackers to read sensitive information from the system memory.

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Computer Exploit Examples In-Depth

1. Morris Worm (1988) – The Dawn of a New Threat

In the twilight of November 2, 1988, the world of computing was taken by storm. A digital menace, the first of its kind, had slipped into the matrix, marking the inception of a new era of cyber threats. The Morris Worm had been unleashed, and within a span of 24 hours, it had burrowed its way into approximately 6,000 computers, which was nearly 10% of the Internet back then.

The mastermind behind this cyber onslaught was none other than Robert Tappan Morris, a young graduate student from Cornell University. His intention wasn’t malicious; he merely wanted to gauge the size of the internet. Unfortunately, a miscalculation in the worm’s code led to its rapid replication, turning it from a harmless experiment into a debilitating attack.

The worm’s victims spanned universities, research labs, military sites, and other organizations with a Unix-based infrastructure. Although the damage was primarily operational, disrupting regular activities and slowing down systems, the estimated cost to remove the worm ranged from $200 to more than $53,000 per institution, causing a total financial loss in the range of $10-100 million.

The exploited data was not personal or financial but rather the vulnerabilities in Unix sendmail, finger, and rsh/rexec. The worm’s aftermath sparked a wave of concern, leading to significant efforts in bolstering computer security and the formation of the first Computer Emergency Response Team (CERT).

The Morris Worm was a wake-up call, and its creator didn’t escape unpunished. Morris was convicted under the Computer Fraud and Abuse Act in 1990, making him the first person to be indicted under this law. His sentence: three years of probation, 400 hours of community service, and a fine of $10,050.

2. Code Red (2001) – The Worm that Shook the World

July 13, 2001, saw the birth of a cyber terror named “Code Red.” This malicious worm wriggled its way through cyberspace, causing havoc for weeks. Exploiting a buffer overflow vulnerability in Microsoft’s Internet Information Services (IIS) web server, it left a trail of chaos affecting over 359,000 hosts worldwide.

The perpetrators behind Code Red remain unknown. But their creation had a significant impact, paralyzing a wide range of entities from businesses to governments. The worm was indiscriminate, hitting targets globally, but the United States bore the brunt, with over 62% of the infected computers.

The damage was not merely operational. The financial toll was staggering, with the total cost of the attack estimated to be a whopping $2.6 billion. This included the expenses incurred for checking systems, installing patches, and recovering from the attack.

Although Code Red didn’t compromise personal or financial data, it defaced affected websites, displaying the message, “Hacked By Chinese!” Its more significant threat, however, was its ability to launch denial-of-service attacks, which could bring down targeted networks.

The tech world rallied to combat Code Red. Microsoft released a patch to fix the exploited vulnerability, and administrators worldwide worked overtime to update their systems. By August, the worm was largely under control, but its legacy lived on, prompting a stronger focus on cybersecurity.

As for legal consequences, none could be pursued due to the anonymity of the worm’s creators. Code Red was a stark reminder of the anonymous threats lurking in the digital shadows, forever changing how we approach cybersecurity.

3. SQL Slammer (2003) – The Lightning Strike

Imagine a bolt of lightning, intense and quick. Now imagine that in cyberspace. That was the SQL Slammer worm, striking the digital world on January 25, 2003. In just about 10 minutes, it had infected approximately 75,000 hosts, nearly half of the susceptible hosts worldwide.

The creator of SQL Slammer remains a mystery, but the worm’s efficiency and speed were a clear indicator of the increasing sophistication of cyber threats. It exploited a buffer overflow vulnerability in Microsoft’s SQL Server and Desktop Engine database products, impacting businesses, governments, and even some individuals globally.

The financial damage was considerable, with estimates ranging up to $1.2 billion worldwide. This included both the immediate costs of dealing with the infection and the long-term costs of upgrading and securing systems to prevent similar attacks in the future.

Although SQL Slammer did not directly compromise personal or financial data, its rapid propagation resulted in widespread network congestion and even complete denial of service for many users, disrupting everything from ATM services to airline flights.

In the aftermath, Microsoft released patches to close the exploited vulnerability. The episode underscored the importance of regular system updates and led to a more proactive approach to patching in many organizations.

Despite the extensive damage caused, there were no legal consequences as the originators of SQL Slammer were never identified. This event served as a stark reminder of the persistent anonymity in the digital realm.

4. Sasser (2004) – The Worm that Made Computers Crash

On April 30, 2004, a new cyber threat emerged, intent on disruption. The Sasser worm, unlike its predecessors, did not require human interaction to spread. It exploited a vulnerability in Microsoft’s Local Security Authority Subsystem Service (LSASS), causing infected systems to crash and reboot, resulting in significant disruption.

Behind this worm was an unlikely perpetrator: a 17-year-old German student named Sven Jaschan. His creation rapidly spread across the globe, affecting hundreds of thousands of computers, from individual PCs to large corporate networks, and even causing several airlines and news agencies to cancel flights and broadcasts.

The worm caused significant financial damage, with estimates ranging from several hundred million to over a billion dollars in lost productivity and system repair costs. The worm also caused operational havoc, disrupting businesses and public services by making systems unusable.

Sasser did not compromise any data, but its impact on system availability caused wide-scale inconvenience and financial losses. Following the attack, Microsoft released a tool to remove the Sasser worm, and an update to patch the vulnerability. This incident prompted many organizations to reevaluate their security practices, emphasizing the importance of timely software updates.

The aftermath of the Sasser worm also had a unique twist. Jaschan was arrested and tried in Germany, where he confessed to creating the worm. He was sentenced to a suspended jail term of 21 months and community service. The Sasser incident highlighted the global nature of cyber threats and the potential for anyone, regardless of age or motive, to cause significant disruption.

5. Conficker (2008) – The Stubborn Worm

On November 21, 2008, a worm named Conficker, also known as Downup or Downadup, began to slither its way through the world’s computer systems. This worm was stubborn, continuing to affect systems for several years after its first appearance.

The creators of Conficker remain unknown. However, their creation exploited a vulnerability in Microsoft’s Windows operating system to create a botnet – a network of infected computers that could be controlled remotely. This botnet spread across the globe, reaching into the systems of individuals, businesses, and governments alike.

The financial damage caused by Conficker was enormous, with estimates reaching up to $9 billion. This estimate includes the costs of cleaning infected systems and the lost productivity from the disruption it caused.

Conficker did not compromise personal or financial data directly. Instead, it was used to install malicious software that could be used to steal sensitive information or launch attacks on other systems. In its wake, Microsoft issued a patch to fix the exploited vulnerability and even placed a bounty of $250,000 for information leading to the conviction of Conficker’s authors, but they were never found.

The Conficker worm is a cautionary tale of the resilience of some cyber threats, and the need for constant vigilance and timely system updates to protect against them.

6. Stuxnet (2010) – The Silent Saboteur

In 2010, a new type of cyber weapon was silently unleashed onto the world stage. Named Stuxnet, this worm was not just an exploit; it was a precisely engineered digital missile, believed to have been developed by the United States and Israel, aimed directly at Iran’s nuclear program.

Stuxnet targeted programmable logic controllers (PLCs) used in industrial automation, specifically those controlling centrifuges for separating nuclear material. This cyber weapon was an international game-changer, demonstrating how cyber attacks could cause physical damage.

The financial costs of Stuxnet are difficult to estimate, but the worm set Iran’s nuclear ambitions back by several months, according to some reports. The geopolitical ramifications were, however, much more significant.

Stuxnet didn’t compromise personal or financial data. Instead, it caused the centrifuges to spin out of control, while displaying normal operation to monitoring systems, thus physically damaging the equipment.

The aftermath of Stuxnet was a new awareness of the potential for cyber warfare, prompting nations worldwide to invest heavily in cybersecurity defenses. Despite the scale and impact of Stuxnet, no legal consequences were ever pursued, as the suspected state actors behind it were never officially confirmed.

The story of Stuxnet serves as a chilling reminder of the potential power and reach of state-sponsored cyber warfare, forever altering the landscape of international security.

7. Heartbleed (2014)- The Bleeding Heart of the Internet

April 2014 unveiled a vulnerability that made the internet’s heart bleed. Aptly named “Heartbleed,” this bug exploited a weakness in the OpenSSL cryptographic software library, a technology used to secure communications on the internet.

The identity of the perpetrators who first exploited Heartbleed is unknown. However, the potential impact was vast, with the bug affecting a significant portion of the web, touching individuals, businesses, and governments alike.

Heartbleed could have led to massive financial losses, but the actual extent is hard to quantify. The bug allowed attackers to read protected information, potentially exposing passwords, financial data, and other sensitive information. It was akin to having a secure vault, but with a backdoor left ajar.

The aftermath of Heartbleed saw a flurry of activity. System administrators rushed to patch their systems, users were urged to change passwords, and companies reviewed their use of OpenSSL. It was a wake-up call for the tech world, highlighting the importance of regular audits and updates of cryptographic software.

Despite the wide-reaching implications of Heartbleed, no legal consequences were applied since there was no specific individual or group identified as being responsible for exploiting the vulnerability. Heartbleed is a stark reminder of the fragile nature of trust on the internet and the need for robust security measures.

8. Shellshock (2014) – The Bash Bug Bombshell

Later in 2014, in September, another significant vulnerability surfaced, this time within Unix-based operating systems. Named “Shellshock,” also known as the “Bash Bug,” it allowed unauthorized users to gain control over an affected system.

Shellshock was an accidental discovery, but it was soon exploited by unknown attackers. The potential impact was global, affecting a broad array of systems from individual computers to major servers since Bash, the vulnerable software, is widely used in many systems.

The financial implications of Shellshock are hard to determine, but it had the potential for significant damage. The bug allowed attackers to take control of systems and execute arbitrary commands, potentially leading to data theft, system hijacking, and a range of other malicious activities.

Following the discovery of Shellshock, patches were quickly released to mitigate the vulnerability. The incident spurred a review of legacy code in many organizations, highlighting the ongoing importance of system updates and security audits.

The Shellshock incident didn’t result in any legal consequences, as the attackers exploiting the vulnerability remain unidentified. It serves as a potent reminder of the need for constant vigilance and proactive security measures in the ever-evolving landscape of cyberspace.

9. Petya/NotPetya (2016/2017) – The Masked Marauder

In June 2017, a devastating cyberattack was launched under the guise of the Petya ransomware, but this was a disguise. The real intent was far more destructive. Dubbed NotPetya, this malware was a wiper, designed not to extort money but to cause maximum disruption and damage.

The main suspect behind NotPetya is the Russian military. Their destructive tool targeted primarily Ukrainian businesses but rapidly spread worldwide, affecting multinational corporations and causing significant disruption.

Financially, NotPetya was one of the most costly cyberattacks in history, with an estimated damage of $10 billion. The malware didn’t just encrypt data; it made the entire system unusable, forcing many businesses to replace their hardware entirely.

In response to NotPetya, software patches and security upgrades were swiftly issued. This event highlighted the importance of keeping systems updated and having robust backup systems in place.

Despite the attribution to the Russian military, there were no direct legal consequences. The NotPetya attack serves as a chilling reminder of the potential for destructive power in the realm of cyber warfare.

10. WannaCry (2017) – The Global Cry of Despair

In May 2017, the world witnessed one of the most widespread ransomware attacks in history. Named WannaCry, this ransomware caused global panic as it encrypted files and displayed a ransom message across screens worldwide.

The attack was linked to the North Korean hacker group, Lazarus. It exploited the EternalBlue vulnerability, affecting systems across sectors, from healthcare to business to government, leading to operations grind to a halt in various organizations.

The financial impact of WannaCry is estimated to be around $4 billion, including the ransom payments, the costs of system recovery, and the losses due to operational disruption.

In the aftermath of WannaCry, patches were hastily applied, and systems were updated. The attack served as a wakeup call, demonstrating the necessity of regular system updates.

Although the attribution to North Korea led to increased international tensions, there were no direct legal consequences. The story of WannaCry serves as a stark reminder of the destructive potential of ransomware attacks.

11. Meltdown/Spectre (2018) – The Ghosts in the Machine

At the beginning of 2018, two critical vulnerabilities were revealed in modern processors. Named Meltdown and Spectre, these vulnerabilities could allow attackers to access sensitive data directly from the processor.

Meltdown and Spectre were not traditional exploits, in the sense that they weren’t pieces of malicious software. Instead, they were design flaws in the very hardware that powers our computers.

The financial impact of Meltdown and Spectre is hard to quantify, but the costs of patching systems and replacing vulnerable hardware worldwide were substantial. The vulnerabilities potentially allowed attackers to access sensitive data, including passwords and encryption keys, directly from the processor.

In response to the discovery of Meltdown and Spectre, processor manufacturers and operating system vendors released patches and updates to mitigate these vulnerabilities. This event led to a reevaluation of processor design and security practices in the tech industry.

The story of Meltdown and Spectre serves as a reminder that security is not just about protecting against malicious software – it also involves ensuring the hardware that powers our devices is secure.


We’ve taken a journey through some of the most notorious exploits in history, from worms that infected millions of computers to state-sponsored cyber weapons. These stories serve as powerful reminders of the potential damage that cyber threats can inflict on individuals, businesses, and nations.

Staying safe in this ever-evolving digital landscape might seem daunting, but there are practical steps you can take. Keeping your devices updated is one of the most effective measures. Updates often include patches for security vulnerabilities that attackers could exploit. Don’t delay when you see that update notification – think of it as a necessary shield in your digital armor.

Investing in good antivirus software for Windows 11 like Norton, Bitdefender, McAfee, Panda, or Kaspersky can also provide an additional layer of protection. These programs can detect and neutralize many threats before they have a chance to cause harm.

But remember, technology alone isn’t enough. Staying informed about the latest threats and understanding how to recognize potential dangers is crucial. Cybersecurity is everyone’s responsibility, and with a little knowledge, we can all contribute to making the digital world a safer place.

For more information, check out these trusted cybersecurity resources:

  1. The United States Computer Emergency Readiness Team (US-CERT)
  2. The Cybersecurity & Infrastructure Security Agency (CISA)
  3. The European Union Agency for Cybersecurity (ENISA)
  4. The National Cyber Security Centre (NCSC) – UK
  5. The Australian Cyber Security Centre (ACSC)

Stay safe, stay updated, and stay informed. Together, we can navigate the challenges of the digital age.

Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor is a Dutch engineer and entrepreneur. He has tested security software since 2014.

Over the years, he has tested most of the best antivirus software for Windows, Mac, Android, and iOS, as well as many VPN providers.

He uses Norton to protect his devices, CyberGhost for his privacy, and Dashlane for his passwords.

This website is hosted on a Digital Ocean server via Cloudways and is built with DIVI on WordPress.

You can find him on LinkedIn or contact him here.

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