Ransomware has grown from being a nuisance for individual users to a national concern for the United States. Over the last few years, attacks have shut down hospitals, disrupted fuel supplies, stalled businesses, and cost organizations billions of dollars. What makes these incidents “biggest” is not just the ransom amounts but the scale of disruption—millions of people unable to access healthcare services, thousands of dealerships unable to sell cars, or an entire region facing fuel shortages.
In this blog, we’ll look at some of the most significant ransomware attacks in the U.S., why they made headlines, and the lessons every business can take away.
Ransomware is no longer just about locking files and demanding payment. Modern attacks combine data theft, system encryption, and public pressure tactics that can bring critical services to a halt. When the target is a hospital network, a fuel pipeline, or a technology provider supporting thousands of businesses, the impact quickly moves from an IT issue to a national problem.
Over the past few years, several ransomware attacks in the U.S. have stood out for their scale, disruption, and lasting impact on critical industries.
In early 2024, Change Healthcare, a subsidiary of UnitedHealth Group, was crippled by a ransomware attack attributed to the ALPHV/BlackCat group. The incident disrupted nationwide insurance claims and pharmacy services, leaving providers unable to process prescriptions or receive payments. Reports suggest that between 190 and 193 million individuals were affected, making it one of the largest healthcare-related breaches in U.S. history. Costs are estimated in the billions, not only in ransom but also in lost revenue, recovery efforts, and provider support.
CDK Global, the software backbone for thousands of auto dealerships, faced a ransomware attack that halted its dealer management systems. Around 15,000 dealerships across the U.S. and Canada were unable to handle sales, financing, or service transactions. The outage lasted for days and triggered significant losses, with industry estimates suggesting the impact exceeded $1 billion. This case showed how one vendor outage can paralyze an entire sector.
In 2023, two of the biggest names in U.S. hospitality were hit almost back-to-back. Caesars Entertainment reportedly paid a $15 million ransom after attackers used social engineering to bypass defenses. MGM Resorts, on the other hand, chose not to pay and suffered widespread outages that disrupted hotel check-ins, casino floors, and digital room keys for weeks. The contrasting responses highlighted the difficult choices companies face when under attack.
The Colonial Pipeline ransomware attack remains one of the most infamous examples of critical infrastructure disruption. In May 2021, the company shut down its operations to contain the breach, leading to fuel shortages and panic buying across the East Coast. Colonial admitted to paying a $4.4 million ransom, though the Department of Justice later recovered $2.3 million of it. This incident brought ransomware into mainstream conversation as a national security issue.
The Kaseya ransomware attack in 2021 exploited vulnerabilities in its VSA remote management software, affecting managed service providers and up to 1,500 downstream businesses worldwide. Many U.S. companies were caught in the ripple effect, experiencing outages and encrypted systems. The attack underscored the devastating potential of supply-chain compromises, where one entry point can multiply damage across hundreds of organizations.
JBS, the world’s largest meat processor, was forced to halt its North American operations after ransomware took key systems offline. The disruption affected meat supply chains, raising concerns about food security. JBS confirmed paying an $11 million ransom to resume operations, making it one of the largest publicly acknowledged ransom payments at the time.
In May 2024, Ascension, one of the largest nonprofit health systems in the U.S., was hit by ransomware that forced hospitals into “downtime procedures” for weeks. Ambulances were diverted, patients faced delays, and electronic health records were inaccessible. Later disclosures confirmed that data of roughly 5.6 million individuals was compromised. The attack reinforced how vulnerable healthcare systems remain and how disruptive ransomware can be to essential services.
Not every ransomware attack makes national headlines. The ones we call the “biggest” share certain characteristics that set them apart. These criteria are useful not only for looking back at past events but also for assessing the potential impact of future incidents within your own organization.
Looking across these high-profile incidents, a few common threads emerge. They highlight not just how ransomware groups operate, but also where organizations are most vulnerable.
Every major ransomware incident in the U.S. has reinforced the same lesson: preparation and rapid response matter more than ransom negotiations. Here’s a practical checklist enterprises can use to reduce exposure and limit damage:
Review vendor connections, enforce least privilege, and require security attestations. A single weak supplier, as seen in the Kaseya and CDK Global cases, can multiply risk across your business.
Conduct tabletop exercises and ensure manual workarounds exist for core operations. Organizations like Ascension and Colonial Pipeline showed how downtime directly impacts customers and revenue.
Use phishing-resistant MFA, privileged access management (PAM), and just-in-time access to limit lateral movement. Social engineering exploited MGM’s help desk—showing human access points are as critical as system defenses.
Keep offline, immutable backups and rehearse recovery procedures. Recovery speed often determines whether downtime lasts hours or weeks.
Deploy EDR, NDR, and SIEM tools with a dedicated SOC team to spot ransomware behaviors early. Rapid isolation can contain what might otherwise become a nationwide disruption.
Be ready to handle breach notifications, regulatory reporting, and customer communications. Delays or missteps here can compound reputational damage long after systems are restored.
At Sattrix, we work with enterprises to stay ahead of ransomware and other advanced threats. Our services go beyond detection—we help organizations build resilience:
The biggest ransomware attacks in the U.S. have shown just how far-reaching these threats can be. Whether it’s millions of patients unable to access care, thousands of dealerships unable to serve customers, or fuel shortages impacting an entire region, the damage extends well beyond the affected company.
For businesses, the lesson is clear: ransomware is not a distant risk—it’s a present and ongoing challenge. By strengthening defenses, preparing for incident response, and working with trusted security partners, enterprises can avoid becoming the next case study.
The Change Healthcare ransomware attack in 2024 is considered the biggest, impacting over 190 million individuals and costing billions in recovery.
In 2025, U.S. enterprises continue to report attacks from groups like LockBit, BlackCat/ALPHV, and Clop, though healthcare and service sectors remain the most targeted.
The Zeus Trojan, first discovered in 2007, is one of the biggest ever—used to steal banking credentials and infect millions of computers worldwide.
Several major U.S. companies have been hit, including Colonial Pipeline, MGM Resorts, JBS Foods, Change Healthcare, and CDK Global.
