From the first internet worm to a hidden backdoor in Linux software, these are the attacks, breaches and flaws that changed how the world thinks about security.
Figures are the most widely reported estimates and may be revised over time. Where an attack has been attributed to a state, the attribution comes from governments and researchers, not from a court verdict.
The list is in date order. For the largest thefts of money and cryptocurrency, see the separate page on the biggest cyber thefts.
The hacks, in date order
- The Morris worm — One of the first internet worms. A bug made it re-infect machines and slow many to a crawl.
- ILOVEYOU worm — An email worm disguised as a love letter that spread worldwide within days.
- Stuxnet — Malware that physically damaged centrifuges in Iran's nuclear program. Widely believed to be a US-Israeli operation, though not officially confirmed.
- PlayStation Network breach — Attackers took personal details from Sony's gaming network, which was offline for weeks.
- Target — Attackers entered through a contractor's credentials and stole payment card details at the checkout.
- Yahoo — Account data was stolen in 2013. The company disclosed it in 2016 and in 2017 said all accounts were affected.
- Sony Pictures — Unreleased films, scripts and emails were leaked. The FBI attributed the attack to North Korea.
- Heartbleed — A flaw in the OpenSSL encryption library let attackers read server memory.
- Mirai botnet — Took over insecure cameras and routers and helped knock the DNS provider Dyn offline.
- Equifax — A known web software flaw was left unpatched and exposed personal and financial data.
- WannaCry — Ransomware that spread through a leaked exploit and hit hospitals, factories and businesses.
- NotPetya — Data-wiping malware disguised as ransomware, spread via a Ukrainian software update.
- SolarWinds — Malicious code hidden in a routine software update reached government agencies and companies.
- Colonial Pipeline — Ransomware led the company to halt fuel deliveries across much of the US East Coast.
- Log4Shell — A flaw in a ubiquitous Java logging library, rated the maximum severity of 10.
- MOVEit — The Clop ransomware gang exploited a flaw in file-transfer software to steal data from many organizations.
- The xz backdoor — A hidden backdoor planted in a compression library by a long-term contributor, caught before it reached most stable systems.
Frequently asked questions
What was the biggest hack ever?
By number of accounts, the 2013 Yahoo breach, which affected all three billion accounts. By cost and disruption, NotPetya and WannaCry are often cited.
What was the first major hack?
The 1988 Morris worm is usually considered the first widely disruptive internet attack.
Which hack was the most sophisticated?
Stuxnet is often called the most sophisticated, because it physically damaged industrial equipment.
Are these numbers exact?
No. They are the commonly reported figures and estimates.