5 Biggest cyberattacks in history that changed the digital security landscape forever

Cyber-attack refers to the intentional application of computer hardware, networks, or systems to cause damage, steal sensitive data, or disrupt normal operations. One lone hacker, a group of sophisticated cybercriminals, or even a nation state could carry out the attacks. As more data and infrastructure get digitised, governments, organisations, and individuals alike are increasingly threatened by cyberattacks in very concrete ways. These cyberattacks can vary from mere disruption to devastating intrusion with economic losses, loss of reputation, and compromised national security.



What is a cyberattack

A cyberattack refers to a deliberate and malicious effort to compromise, harm, disrupt, or steal data from a computer system, network, or device. Such attacks are often conducted by hackers, cybercriminals, or even state actors to realise any number of objectives, including stealing confidential information, causing operational interference, or inflicting monetary damage.




Types of cyber attacks


The two broad types of cyberattacks are those targeting disruption of system and network operations, and those targeting access to sensitive data. An awareness of these types contributes to enhancing defense systems.



Disabling attacks

These are meant to take a computer, network, or system offline, essentially cutting access for those who are authorized to use it. Denial-of-Service (DoS) and Distributed Denial-of-Service (DDoS) are good illustrations. They overwhelm a network with questionable traffic or requests that leave the system unable to handle it and, in the process, crash. Disruption is their primary goal and not theft of information.


Data theft and data breaches
The second largest category is efforts to steal confidential data. It can be financial data, private data, intellectual property, or state secrets. Phishing, malware, and exploitation of systems are familiar methods used by hackers to acquire unauthorized access to systems. After acquisition, burglars resell looted data or use it for criminal intentions, e.g., identity fraud or corporate espionage.



Common hacker techniques


Hackers employ an array of advanced methods and tools for mounting their cyber attacks. Hackers' favorite means are:




Malware

Malware is an umbrella term that refers to any type of bad code with the potential to infect a system and cause mayhem. Viruses, worms, trojans, ransomware, and spyware are a few of the most common types of malware. Malware can steal data, bring down systems, or even hold information for ransom and demand money for its freedom (in ransomware attacks).


Phishing

Phishing is a social engineering attack in which the attackers pretend to be genuine organizations or entities with a purpose of duping the victims into sharing sensitive information such as passwords, usernames, or financial details. Phishing attacks normally are email or imitation websites in nature, coming across as actual websites but rather made for trapping users' information on being clicked.


Social engineering
In social engineering attacks, people are used by hackers to leak sensitive information. They can also pose as coworkers or supervisors for the purpose of gaining the confidence of an individual and trick the victim into lowering security protocols such as revealing log-in details or clicking on unsafe links.


Group attacks

Large-scale cyberattacks are often launched by well-coordinated groups of hackers. The groups will target high-profile entities or government organizations and apply complex methods, including advanced persistent threats (APTs), in order to acquire persistence over a long period.




Growth of cybercrime


Cybercrime is a quick-growing enterprise. In 2017, it lost 780,000 records daily through various cyberattacks, McAfee's Economic Impact of Cyber Crime recorded. The figures indicate the numbers and volumes of cyberattacks mounting. According to the reports, cybercrime is estimated at $10.5 trillion by 2025.

E-mail is still among the most popular attack vectors despite heightened cybersecurity. CSO research indicates that 92% of malware is transmitted through e-mail, most commonly by a malicious link or an attachment within a phishing e-mail. The attackers take advantage of the human factor by tricking people into opening the mail, which in turn leads to unintentional installation of malware on their systems.





Major cyberattacks in the history


In recent years, there have been a number of high-profile cyberattacks that have hit the headlines, detailing just how sophisticated cyber thugs are getting and what security breaches can entail.



Morris Worm (1988)
The Morris Worm was the very first ever recorded mass cyberattack. Written by Robert Tappan Morris, at the time an academic at the graduate level, the worm infects computers at a rapid pace across the net and infects around 6,000 computers. Estimated loss resulting from this worm is anywhere from $10 million to $100 million, giving rise to the added concern about systems that are vulnerable on the net.




MafiaBoy (2000)
One of these 15-year-old Canadian hackers, MafiaBoy, in 2000 launched a DDoS attack on busy websites such as Amazon, CNN, eBay, and Yahoo!. The attack harvested around $1.7 billion worth of losses. The attack highlighted just how simple it is even for novice hackers to make significant disruption using the international internet network.



Google China (2009)

Google's servers were hacked by the hackers in 2009 to access Chinese human rights activists' e-mails. The hacking was believed to have been carried out by China's government, and thus Google shifted its servers to Hong Kong in 2010 as part of its battle against censorship and surveillance.


Jonathan James and the U.S. Department of Defense (1999)
Jonathan James, a computer hacker at age 15, infiltrated the U.S. Department of Defense computers and stole sensitive data, including NASA software worth $1.7 million. The breach resulted in damages of $41,000 and demonstrated that even the most secure government networks could be compromised.



Stuxnet (2010)
The Stuxnet worm was an enormously advanced cyberweapon that attacked the nuclear enrichment facilities of Iran. It dismantled almost 1,000 nuclear centrifuges, slowing down Iran's nuclear ambitions. It is believed widely to have been an American Israeli joint effort, the first use of a cyberattack causing physical damage.




Most famous recent cyber attacks


Cyberattacks do not only affect operational and technical aspects, but they also lead to humongous economic loss. For example, the Melissa Virus was a cost of $1.1 billion in damages worldwide. Furthermore, data breaches, such as when Albert Gonzalez hacked millions of credit card numbers in 2009, were part of one of the biggest history-making credit card scams.


Cyberattacks just keep on rolling, and there are new cyberattacks daily. Some of the most famous recent cyberattacks include:



U.S. Treasury Department Incident (2024)


U.S. Treasury Department networks were attacked in December 2024 by a state-sponsored Chinese attacker, who penetrated employee desktops and sensitive data. The incident was ranked as a high event, which illustrated the threat level of state-sponsored cyber tapping and its impact on national security.



North Korean Crypto Hack (2025)

North Korean cyberthieves hacked into a cryptocurrency exchange and stole $1.5 billion worth of digital currency in the largest cyberattack on record in 2025. This hack illustrates the growing necessity of safeguarding digital assets as attacks mount from highly funded and highly advanced cybercrime.






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