Learn how ransomware attacks work and what you can do to prevent them.
• Ransomware encrypts your files and demands payment for the decryption key
• Modern attackers steal data first, then threaten to leak it if you don’t pay. Some skip encryption entirely
• Most attacks start with stolen credentials, not technical exploits
• Dark web monitoring can detect stolen credentials before ransomware operators exploit them
Ransomware cost organizations $1.1 billion in ransom payments in 2024 alone. That’s just the ransom. Add recovery costs and downtime, and the real toll reaches tens of billions annually.
But understanding how these attacks work is the first step to preventing them.
This guide covers 15 famous ransomware examples and breaks down how each attack happened. You’ll learn the common patterns attackers use and how to protect your organization.
Whether you’re a security professional or business leader trying to understand the threat, these real-world examples show what ransomware looks like in practice.
Ransomware is malicious software that encrypts files on infected systems and demands payment for the decryption key. Modern ransomware steals data before encrypting, giving attackers two forms of leverage: pay or lose your files and have your data leaked. Some groups now skip encryption entirely and just threaten to publish stolen data.
The ransomware business model has evolved significantly. Early ransomware just encrypted files. Today’s operations run like businesses with customer support and negotiation teams.
Ransomware-as-a-Service (RaaS) dominates the landscape. Developers create and maintain the malware. Affiliates handle the actual attacks. They split ransoms, typically 70-80% to affiliates and 20-30% to developers.
According to Chainalysis, ransomware payments exceeded $1.1 billion in 2024. That’s just what victims paid. The total economic impact including downtime and recovery costs reaches far higher.
Ransomware attacks follow a predictable pattern. Understanding each stage helps you detect attacks before encryption.
Stage 1: Initial Access. Attackers need a way in. Stolen credentials are the most common method. Phishing emails come second. Stolen credentials are preferred because they’re quiet and don’t trigger security alerts.
Stage 2: Persistence and Reconnaissance. Once inside, attackers establish persistence so they can return if discovered. They map your network and identify valuable systems. They also locate your backups. This stage can last days or weeks.
Stage 3: Privilege Escalation. Attackers move from their initial foothold to higher-privilege accounts. Domain admin access is the goal. With those credentials, they control your entire environment.
Stage 4: Data Exfiltration. Before encrypting anything, attackers steal sensitive data. Customer records and financial information are common targets. This gives them leverage even if you have backups.
Stage 5: Encryption and Ransom. Finally, attackers deploy ransomware across your network. Systems lock up simultaneously. A ransom note appears demanding payment in cryptocurrency.
The entire process from initial access to encryption typically takes 1-3 weeks. That’s your window to detect and stop the attack.
Ransomware comes in several forms. Each type works differently and requires different responses.
Crypto Ransomware encrypts files using strong encryption algorithms. Without the decryption key, files are unrecoverable. This is the most common type. LockBit and BlackCat/ALPHV are prominent examples.
Locker Ransomware locks users out of their devices entirely. The files aren’t encrypted, but you can’t access them because you can’t log in. This type is less common now because it’s easier to bypass.
Data Theft + Encryption is now the standard approach. Attackers steal your data first, then encrypt your systems. If you don’t pay, they leak your data publicly. Backups won’t save you from the exposure. Some groups like Cl0p now skip encryption entirely and just steal data.
These attacks shaped the ransomware landscape. Each one demonstrates different tactics and vulnerabilities.
WannaCry remains the most famous ransomware attack in history. In May 2017, it infected over 200,000 computers across 150 countries in just a few days.
How it worked: WannaCry exploited EternalBlue, a Windows vulnerability leaked from the NSA. It spread automatically across networks without user interaction. One infected machine could compromise an entire organization.
Impact: The UK’s National Health Service was hit hard. Hospitals turned away patients. Ambulances were diverted. Globally, damages reached an estimated $4-8 billion.
Key lesson: Patching matters. Microsoft had released a fix two months before the attack. Organizations that patched were protected.
NotPetya caused more damage than any other cyberattack in history. It masqueraded as ransomware but was actually a destructive wiper designed to cause maximum harm.
How it worked: Attackers compromised a Ukrainian accounting software called M.E.Doc. A malicious update spread NotPetya to every company using the software. From there, it spread globally through corporate networks.
Impact: Maersk, the shipping giant, lost nearly all its IT infrastructure. FedEx subsidiary TNT Express suffered $400 million in damages. Total global damage exceeded $10 billion.
Key lesson: Supply chain attacks have far-reaching impact. One compromised vendor affected thousands of organizations worldwide.
The Colonial Pipeline attack showed how ransomware can threaten critical infrastructure. It triggered fuel shortages across the U.S. East Coast.
How it worked: Attackers accessed Colonial’s network through a compromised VPN account. The password had been exposed in a previous breach. There was no multi-factor authentication.
Impact: Colonial shut down 5,500 miles of pipeline supplying 45% of East Coast fuel. Panic buying caused gas station shortages. Colonial paid a $4.4 million ransom (later partially recovered by the FBI).
Key lesson: Leaked credentials are dangerous. A single exposed password led to a national emergency. Credential monitoring could have detected the exposure before attackers exploited it.
The Kaseya attack demonstrated how attacking a single vendor can compromise thousands of downstream customers simultaneously.
How it worked: REvil exploited vulnerabilities in Kaseya’s VSA remote management software. Managed service providers (MSPs) using the software pushed ransomware to all their clients unknowingly.
Impact: Between 800 and 1,500 businesses were affected globally. Swedish grocery chain Coop had to close 800 stores when their point-of-sale systems went down.
Key lesson: One compromised vendor can take down thousands of customers.
The Change Healthcare attack disrupted the entire U.S. healthcare payment system. It’s one of the most consequential ransomware attacks ever.
How it worked: ALPHV/BlackCat accessed Change Healthcare through stolen credentials. The targeted Citrix portal lacked multi-factor authentication. Attackers stole 4TB of data before encrypting systems.
Impact: Pharmacies couldn’t process prescriptions. Hospitals couldn’t verify insurance. Healthcare providers went weeks without payment. UnitedHealth Group reported $872 million in direct costs.
Key lesson: Credential hygiene is critical. MFA on all remote access could have prevented this attack entirely.
The MOVEit campaign showed how a single zero-day vulnerability can affect hundreds of organizations simultaneously.
How it worked: Cl0p exploited a SQL injection vulnerability in MOVEit file transfer software. They stole data from hundreds of organizations before anyone knew about the vulnerability.
Impact: Over 2,500 organizations were affected. Government agencies and universities were hit hard. Millions of individuals had personal data exposed.
Key lesson: File transfer systems are high-value targets. They often hold sensitive data from multiple parties.
The MGM attack demonstrated how social engineering combined with credential theft can bypass strong security controls.
How it worked: Scattered Spider called MGM’s IT help desk pretending to be an employee. They convinced the help desk to reset credentials. From there, they deployed ALPHV ransomware.
Impact: MGM’s Las Vegas properties went offline. Guests couldn’t use room keys or slot machines. The company lost an estimated $100 million.
Key lesson: Social engineering remains effective. Technical security means nothing if attackers can talk their way in.
Caesars was attacked by the same group as MGM but chose a different response.
How it worked: Scattered Spider used similar social engineering tactics to gain initial access. They threatened to release stolen customer data.
Impact: Caesars reportedly paid a $15 million ransom to prevent data disclosure. They disclosed the breach but avoided the operational disruption MGM experienced.
Key lesson: There’s no good option once attackers are in. Prevention is far cheaper than response.
The Costa Rica attack marked the first time ransomware was used to effectively cripple a national government.
How it worked: Conti gained access to government systems and encrypted critical infrastructure. When Costa Rica refused to pay, they published stolen data and demanded a larger ransom.
Impact: Costa Rica declared a national emergency. Tax collection stopped. Foreign trade was disrupted. The government estimated $30 million per day in losses.
Key lesson: Ransomware has become a national security threat. Critical infrastructure requires heightened protection.
The JBS attack threatened food supply chains and showed how ransomware can affect physical-world operations.
How it worked: REvil compromised JBS, the world’s largest meat processor. The attack forced the company to shut down operations across multiple countries.
Impact: JBS paid an $11 million ransom to restore operations quickly. The attack temporarily disrupted meat supply chains in the U.S. and Australia.
Key lesson: Operational technology environments are increasingly targeted. Ransomware has moved beyond just data.
LockBit became the most prolific ransomware operation, responsible for roughly 40% of all attacks at its peak.
How it worked: LockBit operated a well-organized RaaS model with fast encryption and automated attacks. Affiliates could deploy ransomware in minutes after gaining access.
Impact: Thousands of victims globally including Boeing and the UK Royal Mail. LockBit claimed over $120 million in ransom payments.
Key lesson: RaaS has industrialized ransomware. Even low-skill attackers can deploy destructive malware.
Ryuk targeted high-value organizations willing to pay large ransoms. It was known for demanding multi-million dollar payments.
How it worked: Ryuk was typically deployed after initial access through Emotet or TrickBot malware. Attackers would spend weeks inside networks before deploying ransomware.
Impact: Ryuk targeted hospitals and municipalities. Tribune Publishing and Universal Health Services were among the victims.
Key lesson: Healthcare and critical services are deliberately targeted because they’re more likely to pay quickly.
REvil pioneered many techniques that are now standard in ransomware operations.
How it worked: REvil operated as RaaS with a well-developed affiliate program. They pioneered the data leak site model, publicly shaming victims who didn’t pay.
Impact: Major attacks included Kaseya and JBS. The group demanded ransoms up to $70 million.
Key lesson: Ransomware groups learn from each other. Successful tactics spread rapidly across the ecosystem.
Conti was one of the most organized ransomware operations until internal leaks exposed their methods.
How it worked: Conti ran like a corporation with HR departments and salary negotiations. Leaked chats revealed their internal operations in detail.
Impact: Conti attacked healthcare organizations during COVID-19 and eventually targeted the Costa Rican government. Internal leaks eventually led to the group’s dissolution.
Key lesson: Ransomware groups are organized criminal enterprises. They operate with business discipline and hierarchy.
Hive demonstrated how law enforcement can disrupt ransomware operations through patient investigation.
How it worked: Hive operated as RaaS targeting healthcare and critical infrastructure. They stole data before encrypting and published victims on a leak site if they didn’t pay.
Impact: Hive attacked over 1,500 victims and collected over $100 million in ransoms. In January 2023, the FBI infiltrated their infrastructure and provided decryption keys to victims.
Key lesson: Law enforcement is getting better at disrupting ransomware. But new groups constantly emerge to replace those taken down.
Understanding how attackers get in is essential for prevention. The methods have shifted significantly in recent years.
Initial access brokers (IABs) are criminals who specialize in breaking into corporate networks and selling that access to ransomware operators. They obtain credentials through infostealers or phishing. Access typically sells for $500-$5,000 depending on the target’s size and industry.
Stolen credentials have become the primary initial access vector. According to the Verizon DBIR, credentials are involved in the majority of breaches.
Attackers obtain credentials through:
Infostealer malware. Infostealers like RedLine and Vidar harvest credentials from infected devices. They capture browser passwords and session cookies. Session cookies are particularly dangerous because they let attackers bypass MFA entirely. These logs are sold on dark web markets and shared in Telegram channels.
Third-party breaches. Breaches at other companies expose credentials that end up on the dark web. If your employees reused those passwords at work, attackers can use the leaked credentials to access your systems.
The Colonial Pipeline attack started with a single VPN password that appeared in a previous breach. The Change Healthcare attack exploited credentials for a Citrix portal without MFA. These weren’t complex attacks. They were preventable.
Phishing remains effective despite years of security awareness training. Attackers craft convincing emails that trick employees into revealing credentials or running malware.
Modern phishing often targets specific individuals (spear phishing). Attackers research their targets on LinkedIn and craft personalized messages. The MGM attack started with a phone call to the help desk, a form of voice phishing (vishing).
Some ransomware campaigns exploit unpatched vulnerabilities for initial access. The WannaCry attack exploited EternalBlue. The MOVEit attack used a zero-day SQL injection vulnerability.
However, vulnerability exploitation requires more skill than using stolen credentials. Most attackers prefer the easier path.
Prevention starts with understanding how attackers get in. Since stolen credentials are the primary vector, credential security should be your priority.
Monitor for compromised credentials. Dark web monitoring detects when your employees’ credentials appear on criminal marketplaces. You can reset exposed passwords before attackers use them. This is your earliest warning of a potential attack.
Enforce multi-factor authentication. MFA stops most credential-based attacks. Even if attackers have valid passwords, they can’t authenticate without the second factor. MFA isn’t foolproof though. Stolen session tokens can bypass it. Still, prioritize MFA for remote access and privileged accounts.
Maintain offline backups. Backups won’t prevent attacks, but they enable recovery without paying ransom. Keep backups offline or immutable so ransomware can’t encrypt them too.
Patch critical vulnerabilities. WannaCry exploited a vulnerability patched two months earlier. Prioritize patches for internet-facing systems and known exploited vulnerabilities.
Segment your network. Network segmentation limits how far attackers can spread. If ransomware hits one segment, it shouldn’t reach your entire environment.
Train employees. Security awareness training reduces phishing success rates. Focus on recognizing suspicious emails and reporting unusual requests.
Monitor for attacker behavior. Ransomware attacks unfold over days or weeks. Detecting lateral movement or data exfiltration gives you time to respond before encryption.
Ransomware has evolved from simple encryption malware to organized criminal enterprises. The attacks covered here show the real-world impact: hospitals unable to treat patients and fuel shortages across the East Coast.
But they also reveal patterns. Most attacks start with stolen credentials. Most victims lacked basic protections like MFA. Prevention is achievable with the right focus.
Start with credential monitoring. Know when your employees’ passwords appear on criminal marketplaces. Combine that with MFA and offline backups. Employee training helps too.
The organizations that avoid ransomware aren’t lucky. They’re prepared.
Yes, ransomware is a type of malware. It’s malicious software designed to encrypt your files and demand payment for the decryption key. Modern ransomware also steals data before encrypting. If you don’t pay, attackers leak your data publicly.
WannaCry is one of the most damaging real-life malware examples. In 2017, it infected over 200,000 computers across 150 countries. The UK’s National Health Service had to turn away patients. Other notable examples include NotPetya, which caused $10 billion in damages, and infostealer malware like RedLine that harvests passwords from infected devices.
Crypto ransomware is the most common form. It encrypts your files using strong encryption algorithms. Without the decryption key, your data is unrecoverable. Most crypto ransomware now operates as Ransomware-as-a-Service (RaaS), where developers lease their malware to affiliates who conduct attacks.
The 3-2-1 backup rule means keeping three copies of your data on two different storage types with one copy stored offsite or offline. This protects against ransomware because attackers can’t encrypt backups they can’t reach. The offline copy is critical since ransomware actively searches for and encrypts connected backups.
The biggest trend is attackers buying access instead of hacking in themselves. Initial access brokers sell stolen credentials to ransomware operators. Infostealer malware harvests these credentials from infected devices. Dark web monitoring can detect when your credentials appear on criminal markets before ransomware groups exploit them.
Ransomware typically reveals itself through encrypted files with strange extensions and ransom notes demanding payment. But you can detect attacks earlier by monitoring for warning signs. Unusual login activity and mass file modifications are red flags. Compromised credential alerts can warn you before attackers even deploy ransomware.
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