WannaCry Ransomware Attack: What Happened and Is It Still a Threat?

Arsalan Rathore

Arsalan Rathore

September 1, 2025
Updated on September 1, 2025
WannaCry Ransomware Attack: What Happened and Is It Still a Threat?

The WannaCry ransomware outbreak in May 2017 was one of the biggest cyber disasters ever. In just a few hours, it infected over 200,000 computers in more than 150 countries, hitting both businesses and government offices hard. This major attack is estimated to have cost anywhere from 4 to 8 billion dollars, and it really messed things up for critical services like healthcare, transportation, and manufacturing.

What made WannaCry so shocking was how fast it spread and how far it reached. It used a worm-like technique that didn’t need any user action to get around, taking advantage of a known flaw in the Windows Server Message Block protocol. The speed and scale of this attack showed just how dangerous one unpatched vulnerability can be, affecting millions of people and countless organizations all over the globe.

In this blog, you’ll find everything you need to know about WannaCry ransomware and some tips on how to keep yourself safe from these kinds of cyber threats.

What was the WannaCry Ransomware Attack?

WannaCry is a type of ransomware, specifically a cryptoworm, that targets computers running Microsoft Windows. It first appeared on May 12, 2017, and rapidly became one of the most disruptive cyberattacks in history. Within hours, it infected more than 200,000 computers across over 150 countries, affecting private enterprises and public institutions, including the United Kingdom’s National Health Service, automotive manufacturers, and global logistics providers. The financial impact of the attack was estimated to range from hundreds of millions to several billion US dollars.

WannaCry’s ability to self-propagate without any user action made it particularly alarming. Unlike traditional ransomware that relies on victims opening malicious files or links, WannaCry could spread automatically across networks by exploiting a vulnerability in the Windows Server Message Block protocol. 

This flaw, identified as CVE-2017-0144, was associated with the EternalBlue exploit, a tool initially developed by a government intelligence agency and later leaked publicly. Although Microsoft released a critical patch two months prior, many systems remained unprotected because updates were not applied or unsupported operating systems such as Windows XP were still in use.

Once a computer was infected, WannaCry encrypted essential file types, including documents, images, and databases, using a combination of AES and RSA encryption. Victims received a ransom note demanding payment in Bitcoin, initially set at 300 US dollars, with the amount increasing if payment was delayed. The malware displayed a countdown timer, creating pressure to comply before files were permanently lost.

Later the same day, a cybersecurity researcher discovered a kill switch embedded in the ransomware’s code, halting its rapid spread. The researcher prevented further infections by registering a specific domain that WannaCry attempted to contact. However, the damage was already significant, causing operational disruption, data loss, and financial strain worldwide.

How Does a WannaCry Attack Work?

The WannaCry ransomware attack was notable not only for its rapid spread but also for its sophisticated methods of infection and encryption. Understanding how it operates is critical for individuals and organizations seeking to prevent similar attacks.

When WannaCry is introduced into a network, it exploits a vulnerability in the Windows Server Message Block protocol known as EternalBlue. This exploit allows the ransomware to penetrate unpatched systems without requiring user interaction. Once inside a computer, WannaCry scans the local network for other vulnerable machines. This worm-like behavior enables it to propagate automatically, quickly infecting multiple systems within the same network and across connected networks.

After successfully infiltrating a system, the ransomware executes its payload. It scans the device for specific file types, including documents, spreadsheets, images, and databases, and encrypts them using a combination of AES and RSA encryption algorithms. Encryption renders the files inaccessible to the user, effectively locking critical data and essential business information.

Following the encryption process, victims are presented with a ransom note demanding payment in Bitcoin. The initial demand is typically set at 300 US dollars, with instructions for increasing the amount if payment is delayed. The ransomware also includes a countdown timer to create urgency and pressure the victim to pay before the files are permanently lost.

A unique aspect of WannaCry is its inclusion of a kill switch within its code. The ransomware attempts to contact a specific domain; if the domain is registered, it stops spreading. This feature was accidentally discovered by a cybersecurity researcher, who registered the domain and effectively halted the rapid propagation of the malware. However, before the kill switch was activated, the ransomware had already caused significant disruption, highlighting the speed and efficiency of its attack mechanisms.

Why Was the WannaCry Attack So Effective

The WannaCry ransomware attack was super effective because of a mix of clever tech tricks, existing security holes, and many people still using old software. A big part of its success came from taking advantage of the EternalBlue vulnerability in the Windows Server Message Block protocol. This flaw let the ransomware spread automatically between systems that hadn’t been updated, kind of like a worm, which helped it reach computers everywhere really fast.

Another reason it spread so widely was that many organizations, especially in healthcare, manufacturing, and public services, were still using older versions of Windows, like Windows XP, which hadn’t been getting security updates for a long time. Without timely updates, the malware was easy to infect many machines.

WannaCry also had some strong encryption up its sleeve. It used AES and RSA algorithms to lock files in a way that made it almost impossible to recover them without the decryption key. Plus, it added a countdown timer and increased the ransom over time, which put a lot of pressure on victims to pay up quickly.

Impact and Aftermath of WannaCry

  • Over 200,000 computers in more than 150 countries, including hospitals, manufacturing plants, and logistics companies, were affected.
  • Critical services such as surgeries, transportation, and production lines were delayed or halted.
  • Estimated costs ranged from four to eight billion US dollars, including recovery, lost productivity, and reputational damage.
  • Organizations implemented stronger patch management, network segmentation, and employee training programs.
  • The attack highlighted the importance of using VPNs and other network security measures to reduce exposure to malicious traffic.
  • Governments and industries invested in improved cybersecurity infrastructure and threat intelligence programs.

Is WannaCry ransomware attack still a threat?

WannaCry itself is no longer the massive global threat it was in 2017, as Microsoft patched the exploited vulnerability. However, its variants and similar ransomware families still pose risks today.

How to Protect Yourself from such Cyber threats?

Here are some of the ways you can protect yourself from such ransomware attacks:

Keep Software and Systems Updated

Ransomware like WannaCry takes advantage of known weaknesses in operating systems and applications. To defend against these attacks, it is crucial to apply updates and security patches as soon as they are available. 

This means keeping operating systems, web browsers, plugins, and all critical software up to date. Organizations should also upgrade or isolate legacy systems from networks if they no longer receive updates, as these outdated systems are key targets for ransomware.

Use Reliable Antivirus and Anti-Malware

Modern antivirus and anti-malware solutions are designed to detect suspicious behavior, including ransomware activities, before they can execute. These tools provide real-time protection against known malware signatures and heuristic-based detection for new threats. Regularly scanning devices and enabling automatic updates ensures the system can respond to evolving ransomware threats.

Backup Your Data Regularly

Backing up your data is crucial for recovering from ransomware attacks without paying a ransom. You should back up your data often and keep it stored offline and in secure cloud storage. It’s also important to test your backups regularly to make sure your data is safe and that you can restore it easily. This approach helps reduce downtime and prevent permanent data loss.

Implement Network Segmentation

Dividing networks into separate segments helps prevent ransomware from spreading. Critical systems, sensitive data, and operational networks must be isolated. This way, any infection can be contained within a limited area. When combined with strict access controls, network segmentation can significantly reduce the overall impact of an attack.

Use Strong Passwords and Multi-Factor Authentication

Weak passwords are an easy way for cybercriminals to break into systems. Strong and unique passwords and multi-factor authentication make it harder for attackers to get access. Multi-factor authentication adds extra security by requiring a second step, like a one-time code or a fingerprint, even if the password is stolen.

Be Cautious with Emails and Downloads

Phishing emails are a common way to deliver ransomware. Users should carefully check email senders, avoid opening suspicious attachments, and not click on unknown links. Organizations can also use email filtering, URL scanning, and attachment sandboxing to help prevent malware from entering the network through email.

Secure Your Network with a VPN

A VPN encrypts internet traffic, providing a secure tunnel for data transfer and reducing exposure to malicious actors. Use AstrillVPN as it can prevent attackers from intercepting sensitive information, accessing unprotected endpoints, or exploiting vulnerabilities in unencrypted networks. For remote workers, AstrillVPN ensures secure connectivity to corporate networks.

Educate Employees and Users

Human error is often the weakest link in cybersecurity. Comprehensive training programs should teach employees to recognize suspicious activity, report potential threats, and follow best device and data security practices. Awareness campaigns should be ongoing, as cybercriminals continually adapt their tactics.

Monitor Systems for Unusual Activity

Monitoring network traffic, file access patterns, and system behavior is critical for early ransomware detection. Unusual spikes in network activity, unexpected encryption processes, or unauthorized file modifications can indicate an infection. Early identification allows organizations to respond quickly, isolate affected systems, and prevent further damage.

Conclusion

The WannaCry ransomware attack is definitely one of the biggest wake-up calls in cybersecurity we’ve seen lately. It showed just how fast vulnerabilities can be taken advantage of and how far-reaching the fallout can be. Hundreds of thousands of computers around the world were affected, services were disrupted, and it led to billions in losses.

This attack really highlights why being proactive about cybersecurity is crucial. Regularly updating systems, keeping secure backups, watching for unusual activity on networks, and educating users are key defenses against ransomware. Using VPNs also helps by encrypting your internet traffic and cutting down your risk exposure.

In the end, WannaCry reminds us that cybersecurity isn’t something we can skip. Being alert, using a multi-layered security approach, and getting ready for possible threats can really help people and businesses protect their data, keep things running smoothly, and lessen the blow from future ransomware attacks.

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About The Author

Arsalan Rathore

Arsalan Rathore is a tech geek who loves to pen down his thoughts and views on VPN, cybersecurity technology innovation, entertainment, and social issues. He likes sharing his thoughts about the emerging tech trends in the market and also loves discussing online privacy issues.

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