Top 5 Most Dangerous Cyber Attacks of All Time [Full Story]

Computer Security, Top 10

By TechCommuters / December 2, 2024

Top 5 Most Dangerous Cyber Attacks of All Time

Last updated on May 18th, 2025 at 9:09 am

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The threat of cyberattacks has increased over time, affecting not only government institutions but also small enterprises and respective individuals. The problematic thing is that cybercriminals’ techniques are evolving along with technology, making it increasingly difficult for even the most sophisticated security measures to keep pace and protect your sensitive data from being stolen.

In this blog post, we will explore the backstories, the impact, and the lessons learned of the top five most notorious cyber threats in history. The latest data breaches record revealed approximately 1 billion personal records and ransomware have surpassed in 2025 and are rising.

In this post, travel with us to the not-so-distant past to look at how some of the biggest security incidents of all time went down. So, without further ado, let’s roll back.

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Let’s Look Back At The Most Notorious Cyber Threats of All Time

The following section covers the biggest cyberattacks in history and their lasting impact.

1. The Target Data Breach (2013)

Date: 19^th December 2013

Impact:

Compromised Data: About 40 million credit and debit card numbers were taken, and an additional 70 million customers’ names, addresses, and phone numbers were also taken.
Identity Theft Risks: Millions of consumers now face a far higher risk of identity theft as a result of the disclosure of private data.

The Attack’s Story:

Target’s systems were breached by hackers using credentials from a third-party provider. During the busy holiday shopping season, they gained access to point-of-sale (POS) machines and stole millions of credit and debit card numbers.

Target suffered approximately $200 million in damages as well as a damaged reputation as a result of the hack, which exposed the risks associated with subpar vendor security procedures.

LESSONS LEARNED: Invest in adequate cybersecurity protocols such as network segmentation & data encryption. Ensure your organization adhere to robust security practices which are monitored by third-party vendors. Regular employee training is essential to prevent phishing attacks and implement robust social engineering tactics to prevent initial breaches.

2. The Mirai Botnet Attack (2016)

Date: 21^st October, 2016

Impact:

Internet services were disrupted nationwide.
Impacted well-known websites like Reddit, Spotify, Twitter, and Amazon.
Millions of users in the US and Europe experienced service interruptions as a result of this attack.
Vulnerabilities in Internet of Things (IoT) devices that have been made public.

The Mirai Botnet Attack — Image Source: inetms

The Attack’s Story:

Mirai was created to infect susceptible Internet of Things (IoT) devices, including digital video recorders (DVRs), routers, and IP cameras. The botnet found these devices easily since they frequently had weak default passwords. Once infected, these gadgets became “bots,” which the attackers could operate remotely.

The size of the botnet was its greatest asset. Attackers could initiate enormous DDoS attacks by seizing hundreds of thousands of compromised devices, flooding targeted servers and networks with traffic.

LESSONS LEARNED: Ensure you secure your IoT devices and change passwords regularly to prevent unauthorized access. Continuously monitor your network traffic and take immediate action if you detect any unusual activity which can be a potential botnet attack. You can easily mitigate large-scale attacks by implementing traffic filtering and rate limiting.

3. WannaCry Ransomware (2017)

Date: 12^th May 2017

Impact:

Over 200,000 computers are among the impacted systems.
Financial Cost: Damages were estimated to be over $4 billion.
Consequences: Significant disruptions in several industries, notably the NHS in the United Kingdom.

WannaCry Ransomware (2017) — Image Source: thehackernews

The Attack’s Story:

A flaw in Microsoft Windows was used by the worldwide ransomware assault WannaCry to encrypt data on compromised PCs. In order to decode the file, the attackers wanted payment in Bitcoin. Systems in hospitals, banks, and enterprises closed up, paralyzing them.

The EternalBlue exploit, purportedly created by the NSA and released by a hacker collective, was blamed for the attack’s quick spread. Despite attempts to lessen its impact, WannaCry sparked worldwide unrest and brought attention to the weaknesses in unpatched systems.

LESSONS LEARNED: Keep a habit of regularly backing up your data and keep all your software up-to-date with the latest security patches. Educate users about the ransomware and plan out a clear incident response plan. Develop digital hygiene by following safe web browsing habits to reduce the chances of further attacks.

4. NotPetya (2017)

Data: June, 2017

Impact:

Global Reach: NotPetya impacted over 2,300 organizations across more than 60 countries.
Resulted in damages exceeding $10 billion. It affected companies all across the world, with Ukrainian organizations being particularly affected.
Hampered the operations of large corporations like FedEx, Merck, and Maersk.

The Attack’s Story:

Initially posing as ransomware, NotPetya was a destructive wiper malware that caused significant harm all around the world. The assault started with a hacked Ukrainian tax program and quickly expanded across networks using the same EternalBlue flaw that WannaCry took advantage of.

Unlike other ransomware, NotPetya’s main objective was to inflict as much disruption as possible rather than make money. Even if the ransom was paid, the victim’s data would be permanently encrypted once infected, making recovery impossible. The attack highlighted the dangers of supply chain vulnerabilities by destroying Ukraine’s government, banking, and transportation infrastructure and reaching out to multinational firms.

LESSONS LEARNED: Consider prioritizing patch management to address common vulnerabilities. Apply advanced threat detection plan to combat early attacks. Develop and roll out business continuity plans to ensure operational resilience.

5. SolarWinds Supply Chain Attack (2020)

Date: March 2020 (discovered in December 2020)

Impact:

Impacted more than 18,000 SolarWinds clients, including telecom businesses, technology enterprises, and government organizations.
Major private companies like Microsoft, Intel, Cisco, and FireEye. This led to serious data breaches and espionage operations.

solarwinds supply chain attack — Image Source: evalian

The Attack’s Story:

The incident started in September 2019 when threat actors—later identified as APT29 or Nobelium, a Russian espionage group—infiltrated SolarWinds’ network. The attackers introduced malicious code, or a backdoor, into Orion software updates in February 2020. Customers were unaware that this malicious update had been sent to them. Cybersecurity company FireEye initially identified the issue in November 2020 after learning that the malicious updates had affected its systems.

LESSONS LEARNED: Make sure your organization conduct a thorough security assessment before any new integration. Regularly monitor unusual activities in your network and establish solid security frameworks to reduce vulnerabilities. Consider collaborating with multiple organizations to share threat intelligence that can collectively enhance defences against dangerous attacks.

Consider reading our previous article: Guide on Internet Security: How To Protect Yourself Online.

KEY TAKEAWAY:

Well, stronger cybersecurity measures are certainly required as a result of these intrusions, which have revealed weaknesses in our digital infrastructure. Prioritizing security, making significant defence investments, and keeping abreast of emerging threats are all imperative for organizations. People should also take precautions to safeguard their data and adopt safe cybersecurity practices.

Cybercriminals’ strategies will change in tandem with technology. Organizations and individuals need to take a proactive approach to cybersecurity in order to keep ahead of these threats.