The best way to understand cybersecurity is to study real attacks. Each major breach in history teaches lessons that still apply today — about how attackers think, which defences fail, and what organisations should have done differently. Here are five attacks that fundamentally changed how the world approaches digital security.
1. WannaCry Ransomware (2017)
In May 2017, a ransomware attack called WannaCry spread across 150 countries in a single day, infecting over 200,000 computers and causing an estimated $4-8 billion in damage. It hit the UK's National Health Service particularly hard, forcing hospitals to cancel thousands of appointments and divert ambulances.
WannaCry exploited a Windows vulnerability called EternalBlue — a hacking tool that had been developed by the NSA and subsequently leaked by a group called Shadow Brokers. Microsoft had released a patch two months earlier, but most affected organisations had not applied it.
2. The SolarWinds Supply Chain Attack (2020)
In December 2020, it was revealed that hackers — later attributed to Russian state actors — had spent months inside the networks of thousands of organisations including US government agencies, Microsoft, Intel, and Cisco. The attackers had compromised SolarWinds, a software company whose Orion platform was used by 33,000 organisations worldwide.
By inserting malicious code into a legitimate software update, attackers gained access to any organisation that installed the update. The attack went undetected for approximately nine months.
3. The Equifax Data Breach (2017)
In 2017, credit reporting giant Equifax disclosed that attackers had stolen the personal data of 147 million people — including Social Security numbers, birth dates, addresses, and driver's licence numbers. The breach occurred because Equifax failed to patch a known vulnerability in Apache Struts despite a patch being available for months.
The data stolen in this breach continues to be used for identity fraud years later. Equifax paid over $575 million in settlements.
4. The Target Point-of-Sale Attack (2013)
During the 2013 US holiday shopping season, attackers stole credit card data from 40 million Target customers. What makes this attack particularly instructive is the entry point: attackers first compromised a third-party HVAC contractor that had access to Target's network. From there, they moved laterally until they reached the point-of-sale systems.
5. The Colonial Pipeline Ransomware Attack (2021)
In May 2021, Colonial Pipeline — which supplies nearly half the fuel to the US East Coast — was forced to shut down operations after a ransomware attack by the DarkSide group. The attack caused fuel shortages across multiple states. Colonial paid a $4.4 million ransom, though the FBI later recovered a portion of the funds.
The attack succeeded through a single compromised VPN password for an account that was no longer in active use but had never been disabled.
What All Five Have in Common
Looking across all five attacks, the same themes emerge repeatedly: unpatched software, poor access controls, neglected credentials, trusted third parties, and slow detection. None of these attacks required zero-day exploits or nation-state resources to succeed in their initial access phase. They exploited basic security failures that proper hygiene would have prevented.
Understanding how real attacks work is the foundation of effective defence. The best security professionals study breaches obsessively — not to find fault, but to learn and apply those lessons before they face similar situations themselves.