Cyberattacks have exposed billions of personal records, compromised sensitive government and corporate systems, disrupted essential services and caused losses worth billions of dollars. Some of the largest hacks in history have targeted technology companies, financial institutions, telecommunications providers, government agencies and social media platforms. The scale of these incidents is generally measured by the number of accounts or records exposed, the number of people affected, the sensitivity of stolen information and the financial or operational damage caused.
Here are the top 20 biggest hacks in history.
| Rank | Hack or data breach | Year | Estimated records/accounts affected |
| 1. | Chinese surveillance database exposure | 2025 | 4 billion |
| 2. | Yahoo data breach | 2013 | 3 billion |
| 3. | National Public Data breach | 2023-2024 | 2.9 billion |
| 4. | Real Estate Wealth Network exposure | 2023 | 1.5 billion |
| 5. | Aadhaar database exposure | 2018 | 1.1 billion |
| 6. | Alibaba Taobao data scraping incident | 2019 | 1.1 billion |
| 7. | First American Financial data exposure | 2019 | 885 million |
| 8. | LinkedIn data scraping incident | 2021 | 700 million |
| 9. | Sina Weibo data breach | 2020 | 538 million |
| 10. | Facebook data leak | 2019 | 533 million |
| 11. | Marriott / Starwood data breach | 2014-2018 | 500 million |
| 12. | Yahoo data breach | 2014 | 500 million |
| 13. | Adult Friend Finder breach | 2016 | 412 million |
| 14. | MySpace data breach | 2013 | 360 million |
| 15. | NetEase data breach | 2015 | 235 million |
| 16. | Court Ventures / Experian breach | 2013 | 200 million |
| 17. | LinkedIn data breach | 2012 | 165 million |
| 18. | Dubsmash data breach | 2018 | 162 million |
| 19. | Equifax data breach | 2017 | 159 million |
| 20. | Adobe data breach | 2013 | 153 million |
