The Biggest Cyber Attacks in History: A Comprehensive Guide

Cyber attacks have been on the rise in recent years, with hackers & cyber criminals using increasingly sophisticated methods to breach computer systems & networks around the world. Some of these attacks have resulted in massive data breaches, financial losses & disruptions to business operations.

In this comprehensive guide, we will look at some of the biggest cyber attacks in history, exploring the tactics used, damage caused, & lessons learned. Understanding the biggest cyber attacks in history can help organisations & individuals better defend against future threats.

What Constitutes a Major Cyber Attack?

For an attack to be considered one of the biggest cyber attacks in history, it typically meets the following criteria:

• A large number of victims: The attack compromised the data or systems of a substantial number of individuals, companies or government agencies.
• High financial impact: The attack resulted in sizeable financial losses for the victims or gains for the attackers. Major costs stem from recovery efforts, legal liabilities & loss of revenue.
• Significant disruption: The attack led to major disruptions in business operations, manufacturing, infrastructure systems & military capabilities.
• Geopolitical implications: The attack heightened geopolitical tensions, damaged international relations or elicited government sanctions.
• Advanced or novel techniques: The attack demonstrated technical sophistication & marked an evolution in cyber attack methodologies.
• High media coverage: The incident garnered significant mainstream media attention & public concern due to its scale & impact.

Some of the Biggest Cyber Attacks in History

Here is an overview of some of the biggest cyber attacks in history, in rough chronological order:

Morris Worm (1988)

• One of the first major cyberattacks, this early computer worm infected around 10% of computers connected to the early Internet at the time.
• Created by graduate student Robert Morris, the worm did not damage or destroy data but overwhelmed many systems by rapidly propagating & disrupting normal functioning.
• While not intentionally malicious, it highlighted the vulnerability of networked systems & the potential for unintended damage from malware.

Solar Sunrise (1998)

• This coordinated attack from hackers allegedly working for Saddam Hussein in Iraq targeted U.S. military networks, including many unclassified Defence Department systems.
• The attackers probed & mapped military networks to gather sensitive information related to troop deployments, equipment & critical infrastructure.
• The Pentagon spent over $1.5 million responding to the incident & shoring up its network security against future attacks.

Melissa Virus (1999)

• This virus spread via infected Microsoft Word documents emailed as attachments, affecting private sector systems worldwide.
• It spread rapidly, eventually reaching hundreds of thousands of computer systems & causing an estimated $80 million USD in damages.
• The virus marked one of the first widespread “macro viruses” to exploit the Microsoft Word formatting functionality.

ILOVEYOU Virus (2000)

• One of the most virulent early cyber attacks, this virus spread to millions of Windows PCs worldwide within hours of its release.
• Purporting to be a love letter, it arrived as an email attachment that – when opened – forwarded itself to all contacts & replaced files on the victim’s system.
• It ultimately caused around $15 billion USD in damages across the globe, taking down vital government systems like that of the British Parliament.

Code Red Worm (2001)

• Exploiting a vulnerability in Microsoft’s IIS web servers, this worm could spread from system to system without user action, ultimately compromising over 1 million servers.
• Although designed to launch Distributed Denial of Service (DDoS) attacks, the worm’s rapid propagation overwhelmed systems & disrupted connectivity for many organisations.
• It prompted Microsoft to shift to adopt a regular patch release cycle to proactively defend against emerging threats.

SQL Slammer Worm (2003)

• This extremely fast-spreading worm doubled in size every 8.5 seconds at its peak, compromising at least 75,000 systems & causing widespread outages.
• It exploited a flaw in Microsoft’s SQL Server & was designed to degrade system performance.
• Major disruptions included crashed airline reservation systems, disrupted Bank of America (BoA) ATMs & a shutdown of Seattle 911 emergency response systems.

Zeus Trojan (2007-2010)

• A powerful banking trojan, Zeus infected over 3.6 million computers used primarily for financial fraud & identity theft.
• The malware covertly captured banking credentials through key-logging & web injections, enabling fraudulent wire transfers.
• Losses from Zeus exceeded $70 million USD. The source code leaked in 2011, allowing the malware’s rapid evolution & myriad variants to persist through the present day.

Conficker Worm (2008)

• This worm proliferated through a variety of sophisticated propagation techniques, including exploiting weaknesses in Windows operating systems & dictionary password attacks.
• It was estimated to have infected over 9 million Windows systems at its peak.
• It leveraged its botnet capabilities for criminal ends like credential theft, Distributed Denial of Service (DDoS) attacks & financial fraud.

Operation Aurora (2009)

• This cyber attack targeted dozens of organisations to steal Intellectual Property (IP), proprietary data & email credentials. Major victims included Google, Adobe & other Fortune 500 firms.
• The attackers exploited zero-day vulnerabilities in Internet Explorer & installed backdoors for long-term access & data exfiltration.
• Attackers breached the systems of at least 34 companies, making it one of the most far-reaching cyber espionage campaigns to date.

Stuxnet Worm (2010)

• Stuxnet was a highly sophisticated cyber weapon designed to sabotage Iranian nuclear facilities by targeting specific SCADA industrial control systems.
• The worm used multiple zero-day exploits & showed technical expertise far surpassing typical cybercriminals.
• While neither Israel nor the United States has officially acknowledged creating Stuxnet, most experts believe it was a joint effort by both nations as a nonviolent deterrent and is considered to be one of the biggest cyber attacks in history.

RSA Breach (2011)

• Threat actors compromised the network of RSA Security to obtain information related to their SecurID Two-factor Authentication (2FA) products.
• Possessing this data enabled the hackers to impersonate legitimate users & gain access to numerous defence contractors in a subsequent campaign.
• The incident underscored the risks of supply chain compromises & manufacturers of security software also falling victim to cyber-attacks.

Shamoon Virus (2012)

• Used against Saudi Aramco, this cyber attack overwrote hard drives on 30,000 computers to render them inoperable at the largest oil producer in the country.
• While a hacktivist group claimed responsibility, analysts also suspected Iranian government involvement behind the politically motivated attack.
• The virus deleted data necessary for Saudi Aramco’s operations, disrupting production & forcing the company to isolate its systems from business networks.

Yahoo! Breach (2013-2014)

• In what was then the largest data breach in history, threat actors compromised Yahoo!’s network to steal data on all 3 billion of its user accounts.
• The attackers gained access through spear-phishing & exploitation of Yahoo! employees.
• The information exposed in the breach included names, email addresses, phone numbers, birthdates, password hashes & some encrypted passwords.

Target Breach (2013)

• Retail giant Target fell victim to a breach compromising 40 million credit & debit card numbers from in-store customers.
• The attackers first breached a third-party HVAC contractor to pivot into Target’s more vulnerable corporate network.
• News of the breach caused Target’s profits to plummet 46% in the final quarter of 2013. The company ultimately suffered $162 million USD in net expenses responding to the incident.

Anthem Breach (2013-2014)

• Hackers breached U.S. health insurance provider Anthem, stealing personal information related to 80 million customers & employees.
• Data exfiltrated included names, Social Security numbers (SSN), birthdays, addresses, email addresses & employment details.
• The breach highlighted vulnerabilities in the healthcare sector & the value of stolen medical data. Records could allow fraud or enable hackers to craft personalised phishing messages.

Office of Personnel Management Breach (2013-2015)

• Chinese hackers compromised the U.S. government’s OPM network, stealing sensitive data from security clearance investigations on 21.5 million current & former federal employees or contractors.
• Compromised data included Social Security numbers (SSN), residency & educational history, financial history, fingerprints, passwords & even information from interviews with friends & family.
• The extensive personal data has far-reaching implications for identity theft, profiling government employees & cyber espionage.

Bangladesh Bank Heist (2016)

• Hackers attempted to steal nearly $1 billion USD from Bangladesh’s central bank in one of the biggest bank heists in history.
• They obtained valid SWIFT bank credentials through a compromised third-party bank & submitted dozens of fraudulent money transfer requests.
• While most requests were blocked, over $80 million USD was still ultimately stolen.

WannaCry Ransomware (2017)

• WannaCry ransomware propagated rapidly worldwide across hundreds of thousands of computers by exploiting a just-disclosed Windows vulnerability from the ShadowBrokers NSA tool leak.
• The self-replicating crypto worm encrypted Windows systems & demanded ransom payments in Bitcoin to unlock devices.
• WannaCry notably crippled National Health Service (NHS) hospitals in the U.K., hampering operations & diverting ambulances for days. Total damages reached billions.
• WannaCry Attack is considered one of the biggest cyber attacks in history due to the sheer volume of infected systems and the damages caused.

NotPetya Supply Chain Attack (2017)

• Hackers backdoored accounting software MEDoc used extensively in Ukraine to propagate destructive NotPetya malware disguised as ransomware.
• NotPetya rapidly infected multinational companies via their Ukrainian subsidiaries, ultimately inflicting over $10 billion total in damages.
• Maersk, FedEx, Merck, Mondelez & many other Fortune 500 companies had major operations disrupted by compromised Windows systems & data destruction.

SolarWinds Supply Chain Hack (2020)

• Russian state hackers Trojanised software updates for IT management tool SolarWinds Orion, granting access to customer systems after updates were installed.
• U.S. federal agencies like the DHS, Pentagon, Treasury & more were compromised via downstream SolarWinds software, enabling a breach of additional connected systems.
• By leveraging supply chain vulnerabilities, Russia exploited systemic trust in third-party software to infiltrate high-value targets.

Colonial Pipeline Ransomware Attack (2021)

• The ransomware group DarkSide infiltrated Colonial Pipeline networks which control fuel transportation infrastructure across the Eastern U.S.
• Fearing even greater consequences, Colonial preemptively shut down pipeline operations to contain the breach, halting fuel supplies. This led to gas shortages, panic buying & price spikes nationwide.
• The disruptive attack highlighted ransomware risks to physical critical infrastructure. Colonial paid $4.4 million USD in Bitcoin to restore systems.
• These incidents all exceeded a billion dollars USD in damages & demonstrated the power of modern cyber threats.

Key Lessons to be learnt from the biggest cyber attacks in history

Major breaches offer cautionary tales for improving organisational cybersecurity:

• Keep all software updated: Unpatched vulnerabilities enable many attacks & exploits. Regular system updates, patching & version upgrade policies are essential.
• Manage identities tightly: Most attacks compromise legitimate user accounts in some manner. Enforce strong authentication & limit excessive account privileges.
• Segment critical systems: Once perimeters are breached, lateral movement allows attackers to advance deeper into networks. Network segmentation & access restrictions can limit total damage.
• Encrypt sensitive data: Cracking encrypted data is much harder for attackers. Require encryption across databases, files, communications & storage.
• Develop robust incident response: Assume a breach may occur eventually regardless of defences. Ensure the ability to rapidly detect, contain & remediate intrusions.
• Diversify vendors: Relying on a single technology provider creates massive supply chain risk if compromised (e.g. SolarWinds). Multi-vendor strategies increase resilience.
• Backup data regularly: Ensure the ability to restore encrypted or damaged data & systems through offshore, air-gapped backups impervious to compromise.

With broad impact potential from cyber incidents, proactive risk management, defence depth & response planning are essential.

Biggest Cyber Attacks in History (By Type)

Here are some of the most severe cyber-attacks categorised by primary attack vector:

Most Notable Infrastructure Attacks

• Stuxnet sabotage of Iranian nuclear facilities
• Repeated power grid blackouts in Ukraine since 2015
• 2013 breach of Bowman Avenue Dam controls in New York

Most Severe Ransomware Attacks

• 2017 NotPetya global ransomware pandemic ($10B damages)
• 2021 Colonial Pipeline attack halting fuel distribution
• 2017 WannaCry self-replicating crypto worm affecting 300k+ systems

Biggest Supply Chain Attacks

• 2020 SolarWinds backdoor compromising US federal agencies
• 2017 NotPetya malware distributed through M.E.Doc software in Ukraine
• 2022 Codecov software supply chain attack impacting 29+ enterprises

Most Audacious State-Sponsored Attacks

• 2020 alleged Russian SVR hack of SolarWinds, FireEye, Microsoft + more
• 2015-16 Chinese theft of 21+ million records from Office of Personnel Management
• 2017 North Korean WannaCry ransomware built on stolen NSA tools

Major Corporate Data Breaches

• 2013-14 Yahoo breach exposing 3+ billion accounts
• 2022 Okta authentication breach impacting hundreds of enterprises
• 2022 T-Mobile data breach exposing data of over 40 million customers

As digital systems & connectivity continue growing, so do potential vulnerabilities exploitable by sophisticated attackers.

Overview of the Biggest Cyber Attacks in History Since 2000

Year	Cyber Attack	Description	Estimated Damage in USD
2010	Stuxnet	Infrastructure malware that sabotaged the Iranian nuclear program	$1 billion+
2013-14	Yahoo Data Breach	All 3+ billion Yahoo accounts compromised	$400+ million losses
2014	eBay Breach	Credentials of 145 million users stolen	$200+ million losses
2013-15	OPM Breach	Personal data of 21+ million federal employees stolen	Intelligence bonanza for China
2016	Bangladesh Central Bank Heist	$81 million stolen via SWIFT system hack	$81+ million stolen
2017	WannaCry Ransomware	Self-replicating crypto worm encrypted 300k+ systems globally	$4+ billion in damages
2017	NotPetya	Supply chain ransomware attacks paralysed multinational companies	$10+ billion damages
2017	Equifax Breach	The sensitive data of 143 million consumers compromised	$1.4+ billion losses
2018	Under Armour Breach	150+ million MyFitnessPal app accounts compromised	$50+ million losses
2019	Capital One Breach	Data of 100+ million credit card applicants stolen	$100+ million fines
2020	SolarWinds Supply Chain Hack	Russian state hackers breached US federal agencies, Microsoft	Major espionage operation
2021	Colonial Pipeline	Ransomware halted U.S. fuel distribution	$4.4 million ransom

This list highlights major breaches across sectors proving no organisation is immune to cyber threats. Prioritising cybersecurity is essential in the modern digital landscape.

Cyber Attack Trends & Statistics

Cyber attacks continue accelerating in frequency, severity, & complexity:

• Cybercrime is expected to inflict $10.5 trillion in total global damages annually by 2025 (Cybersecurity Ventures)
• Ransomware increased 105% in 2021 compared to 2020 (Unit 42)
• Phishing attacks grew 26% in 2021 versus 2020 as the top enterprise threat vector (Proofpoint)
• 90% of data breaches involved phishing or brute-force credentials

Conclusion

Major cyber attacks continue to rise in both frequency & impact, inflicting damage across critical infrastructure, massive corporations & individuals alike. As connectivity & data collection grows ever more central to society, so do vulnerabilities ripe for exploitation.

While defences have certainly matured, threat actors consistently devise new techniques & vectors of compromise. Whether via supply chain infiltration, ransomware, credential theft or direct infrastructure sabotage, attackers have proven highly capable of disrupting operations, stealing billions in assets & even threatening human lives by crippling hospitals.

For organisations, security can no longer be an afterthought. Proactive risk management, ongoing employee training, defence in depth & incident response preparedness are essential. Keeping software patched & updated, managing identities tightly, encrypting sensitive data & segmenting networks can make exploitation vastly harder.

And for individuals, vigilance around phishing & strong password hygiene provide a frontline of defence. But ultimately cyber attacks now pose systemic risks—like climate change or contagion—that require a coordinated global response among both public & private sector stakeholders across technology, policy, intelligence, law enforcement & cross-border jurisdiction.

We have looked at the biggest cyber attacks in history from 1988 to 2021. Massive cyber attacks will continue reshaping geopolitics, economics & regulation in the decades ahead. But with rapid collaboration & innovation, society can hopefully weather the turbulence & emerge more resilient than before.

Frequently Asked Questions (FAQ)

What cyber attack do experts consider most significant?

Many cybersecurity researchers highlight the 2010 Stuxnet attack on Iranian nuclear enrichment facilities as a true watershed moment. The sophisticated U.S.-Israeli state malware marked the first publicly discovered infrastructure attack to cause physical destruction. By taking critical infrastructure in war offline, it represented a cyber “shot heard round the world” that ushered in a new era of kinetic threats which is why it is considered one of the biggest cyber attacks in history

What recent cyber attack caused the most financial damage?

The 2021 ransomware attack on Colonial Pipeline stands out as extremely disruptive & costly. By holding hostage fuel transport systems supplying nearly half the U.S. East Coast’s liquid fuels, it triggered fuel shortages, panic buying & price spikes nationwide until Colonial paid a $4.4 million ransom. With damages reaching billions, the attack demonstrated ransomware’s danger to critical physical infrastructure.