What Is Ransomware and How Did WannaCry Work?
WannaCry: The Global Cyberattack That Shook the World in 2017
In May 2017, millions of users around the world woke up to one of the most frightening digital extortion messages in history. A bright red screen warned that all your files had been encrypted, and you must pay $300 in Bitcoin to get them back — or lose everything forever.
This was the infamous WannaCry Ransomware, one of the most destructive cyberattacks ever launched. Within just a few hours, the malware had infected over 200,000 computers across 150 countries, striking hospitals, corporations, and government institutions worldwide.
📌 What Is Ransomware and How Did WannaCry Work?
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Encrypts a victim’s files
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Blocks access to the system
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Demands payment in exchange for decryption
According to Microsoft’s official SMBv1 security advisory
(https://learn.microsoft.com/en-us/security-updates/securitybulletins/2017/ms17-010),
WannaCry exploited a critical vulnerability in the Server Message Block v1 (SMBv1) file-sharing protocol.
Because millions of devices had not yet installed Microsoft’s security update, the malware spread rapidly across outdated Windows systems.
💥 How the Attack Spread Across the Globe in Hours
WannaCry's massive success was no coincidence. The malware behaved as a self-propagating worm, giving it the ability to:
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Move automatically between devices without user interaction
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Exploit the leaked NSA tool EternalBlue to breach SMB services
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Plant a persistent backdoor called DoublePulsar
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Replicate itself and scan networks for additional targets
BBC’s technology report on the attack:
https://www.bbc.com/news/technology-39901382
The U.S. cybersecurity agency CISA also highlighted that EternalBlue became one of the most dangerous publicly leaked exploits ever released:
https://www.cisa.gov/news-events/alerts/2017/06/14/eternalblue-exploited
🏥 Global Impact: Hospitals, Transport Systems, and Government Agencies
The most heavily affected victims were:
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The UK’s National Health Service (NHS)
which lost over £92 million in operational damage -
Worldwide shipping companies
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Train and transport systems
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Government offices
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Thousands of small businesses
Because WannaCry spread aggressively through internal networks, environments like hospitals, offices, and institutions with large linked systems were particularly vulnerable.
🛑 The Kill Switch: How the Spread Was Stopped
Fortunately, a cybersecurity researcher discovered an unusual behavior:
WannaCry attempted to ping a random domain that did not exist.
When the researcher registered that domain, the malware interpreted the response as an instruction to shut itself down, effectively disabling its global spread.
This became known as the Kill Switch.
However, although the outbreak was stopped…
Over 90% of infected systems remained permanently encrypted.
💰 Tracking the Bitcoin Wallet Used by the Attackers
Analysis of the attacker’s Bitcoin wallet revealed:
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Payments arrived throughout May 2017
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On August 3, 2017, the attackers withdrew 20 Bitcoin
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Worth $365,000 at the time
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Today, the same amount would exceed $1.2 million
And these are just the transactions publicly recorded — the total number of victims was far larger.
🎯 Who Was Behind the Attack?
The United States officially accused the North Korean hacking group Lazarus Group of orchestrating the attack.
Department of Justice announcement:
https://www.justice.gov/opa/pr/us-charges-north-korean-hacker-over-wannacry-attack
Cybersecurity research from Kaspersky also linked the group to later variants like WannaCry 2.0:
https://www.kaspersky.com/blog/wannacry-lazarus/17452/
However, no arrests were made since the suspects are inside North Korea, a country that does not cooperate with international cybercrime extradition.
🖼 Infographic: WannaCry Overview
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Infographic File:
A_detailed_infographic_titled_"WANNA_CRY"_in_large.png
🔐 How to Protect Your Device Today
After the attack, Microsoft advised all Windows users to permanently disable SMBv1.
Official Microsoft documentation:
https://learn.microsoft.com/en-us/windows-server/storage/file-server/troubleshoot/smbv1-not-supported
CISA also recommends:
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Always installing security updates
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Disabling outdated protocols
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Using firewalls and endpoint protection
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Avoiding suspicious email attachments
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Backing up important files regularly
🧩 Internal Links (Short & Clean)
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For more guidance on preventing similar cyberattacks, visit our internal guide:
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