Top 10 Biggest Cybersecurity Breaches of All Time

LinkedIn's 2021 scraping incident exposed data from 700 million profiles—92% of users—including emails and salaries, fueling targeted phishing attacks against professionals and costing firms millions in recovery. unlike National Public Data, it contained no Social Security numbers, limiting direct financial fraud risk while still enabling sophisticated social engineering at scale.

The 2019 Facebook breach exposed over 533 million records — phone numbers, account IDs, and personal data — scraped from Meta's systems where it was used for two-factor authentication. When the dataset resurfaced on hacking forums in 2021, it fueled a wave of SIM-swapping attacks affecting users worldwide. The incident remains a stark reminder that even the largest social networks can fail to protect authentication data.

Equifax's 2017 breach is the most costly privacy violation in history, with an unpatched Apache Struts vulnerability exposing Social Security numbers, birth dates, addresses, and credit card details of 147 million Americans. The resulting FTC settlement totaled $575 million. Beyond the financial penalty, the incident led to criminal indictments of four Chinese military officers, demonstrating that international cybercrime can carry serious consequences.

Hackers attributed to Chinese state-sponsored group APT41 maintained access to Starwood's reservation system for four years, exfiltrating 500 million guest records including passport numbers and encrypted payment data before Marriott's $13.6 billion acquisition in 2018. The breach highlights the risks of delayed detection in complex corporate integrations.

The 2020 SolarWinds attack compromised 18,000 organizations, including the US Treasury and Microsoft, through malicious code inserted into Orion software updates by Russian intelligence agency SVR. The supply-chain attack — active for nine months — was called by Microsoft President Brad Smith "the most sophisticated cyberattack ever conducted." It set a new standard for sophistication in state-sponsored cyberattacks.

The 2021 Colonial Pipeline attack remains the most disruptive ransomware strike on U.S. critical infrastructure, halting operations for six days and triggering gas shortages across the Southeast. The price spike to $3/gallon far exceeded the national average of $2.85 at the time, and the $4.4 million Bitcoin ransom paid to DarkSide—$2.3 million of which was later recovered by the FBI—marks a rare success in ransom retrieval. The incident set a new benchmark for cyberwarfare targeting vital infrastructure, demonstrating how a single attack could paralyze energy supplies for millions.

The 2024 ransomware attack on UnitedHealth Group's Change Healthcare subsidiary disrupted prescription drug processing across the entire U.S. healthcare system for weeks, affecting 94% of all hospitals—a scale 60% greater than the Colonial Pipeline's regional impact. The $22 million ransom paid to the ALPHV/BlackCat group and the exposure of records for approximately 190 million Americans make it the largest healthcare breach ever, outpacing Colonial's medical data exfiltration by a factor of 180. ALPHV/BlackCat's double extortion tactics proved more sophisticated than DarkSide's, with data leaks amplifying the damage beyond operational shutdowns. This incident highlighted the fragility of centralized healthcare IT, as even a single subsidiary's compromise could paralyze critical infrastructure nationwide.