Some breaches were so massive they affected millions of people, shook entire companies, and forced everyone to rethink how we protect information online. Here’s a look at five of the most impactful hacks in history — whether because of the scale, the damage, or the aftermath.
1. Yahoo (2013–2014): the biggest data breach ever recorded
Between 2013 and 2014, Yahoo was hacked twice, compromising over 3 billion accounts. Email addresses, encrypted passwords, birthdates, and security questions were all exposed. The breach wasn’t made public until years later — right when Verizon was about to acquire the company. As a result, Yahoo’s value dropped, and the sale price was reduced by $350 million.
2. Equifax (2017): when your identity gets stolen without you knowing
In 2017, hackers exploited a known vulnerability in Equifax’s systems and accessed personal data of 147 million people. This included Social Security numbers, home addresses, birthdates, and driver’s license numbers. The consequences were huge: lawsuits, executive resignations, and a permanent stain on the company’s reputation.
3. SolarWinds (2020): the spy that walked right in
This attack wasn’t loud, but it was terrifying. Hackers managed to slip malicious code into software updates for Orion, a product by SolarWinds used by government agencies and large corporations. That backdoor was quietly installed in over 18,000 systems. It took months to detect, and by then, attackers had access to some of the most sensitive networks in the U.S. and beyond.
4. WannaCry (2017): the ransomware that shut down hospitals
WannaCry spread like wildfire in just a few hours. It exploited a Windows vulnerability to encrypt files and demanded payment in bitcoin. Over 230,000 computers in 150 countries were locked. The UK’s National Health Service was one of the worst hit — surgeries and appointments had to be canceled due to paralyzed systems.
5. Mt. Gox (2014): the first major blow to crypto
Back in 2014, Mt. Gox was handling over 70% of all bitcoin transactions. Then it got hacked. 850,000 bitcoins were stolen, worth hundreds of millions of dollars at the time. The company filed for bankruptcy, and users lost huge amounts of money. It was a wake-up call for the crypto world, showing just how unprepared some platforms were when it came to security.
Each of these hacks left a permanent mark. Not just because of the stolen data or financial loss — but because they revealed how fragile digital systems can be. Mistakes, delays, or blind trust in internal software can lead to massive consequences. These five cases are a reminder of what happens when security fails.
