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A Ransomware Operation That Keeps Evolving
Medusa ransomware is becoming harder to ignore. What began as a ransomware operation identified in 2021 has now grown into a threat capable of repeatedly exploiting newly disclosed vulnerabilities, purchasing network access from brokers, abusing legitimate administration tools, and striking organizations before defenders have enough time to respond.
An updated joint advisory from the U.S. Cybersecurity and Infrastructure Security Agency (CISA), FBI, and Department of Health and Human Services (HHS) offers a sobering look at how the Medusa ransomware-as-a-service ecosystem operates. The advisory expands on guidance originally released in March 2025 and incorporates information gathered through continuing FBI investigations.
The most striking development is the growth in known victims. The advisory’s count increased from more than 300 victims in March 2025 to more than 500 by April 2026.
That jump is not simply a statistic. It illustrates how ransomware groups are industrializing intrusion operations, combining underground access brokers, rapidly weaponized vulnerabilities, legitimate administrative software, credential theft, data exfiltration, and encryption into a highly efficient criminal business model.
Medusa’s Business Model Is Built Around Access
Medusa does not necessarily need to break into every organization itself. Instead, the group can rely on an underground economy in which initial-access brokers find vulnerable networks and sell or transfer access to ransomware operators.
According to the updated advisory, Medusa actors have paid access brokers anywhere from approximately $100 to $1 million, depending on the value and exclusivity of the access.
The highest payments reportedly go to brokers who work exclusively with Medusa. However, many brokers simultaneously serve multiple ransomware operations or variants.
This arrangement creates an important division of labor. One criminal specializes in finding an exposed system, another maintains access, another steals credentials or data, and the ransomware operation ultimately monetizes the intrusion.
The result is a cybercrime ecosystem that resembles a supply chain.
Speed Has Become One of
One of the most concerning findings in the advisory is Medusa’s ability to move extremely quickly after vulnerabilities become known.
The updated guidance states that Medusa actors have been observed exploiting newly announced vulnerabilities within 24 hours.
Even more concerning, investigators have observed exploitation occurring as much as a week before public vulnerability disclosure.
That does not necessarily mean Medusa develops zero-days itself. In fact, the advisory says there is no indication that the group develops its own zero-day or N-day vulnerabilities.
Instead, the operators appear to acquire advanced access to exploits from unknown sources or rapidly exploit newly disclosed vulnerabilities before organizations have enough time to patch them.
This distinction matters.
Medusa does not necessarily need to discover the next groundbreaking vulnerability. It only needs to be faster than the defenders responsible for patching it.
The Patch Window Is Becoming a Battlefield
For defenders, this creates a dangerous race against the clock.
A vulnerability may be publicly disclosed in the morning. Security teams may receive an advisory shortly afterward. Testing may then be required before a patch can be deployed across thousands of systems.
Meanwhile, attackers may already be scanning the internet for exposed targets.
By the time a company completes its normal change-management process, criminals may already be inside.
This is why modern vulnerability management cannot simply mean maintaining a list of missing patches. Organizations increasingly need to understand which vulnerabilities are being actively exploited, which internet-facing systems are exposed, and how quickly those systems can be remediated.
Fortra GoAnywhere and BeyondTrust Become Part of the Story
The advisory specifically expands its discussion of vulnerabilities exploited by Medusa, including flaws involving Fortra GoAnywhere and BeyondTrust products.
These incidents demonstrate why widely deployed enterprise software can become an attractive gateway for ransomware operators.
A vulnerable remote-access platform, file-transfer system, identity service, or management product can provide an attacker with an initial foothold without requiring a traditional phishing campaign.
Once access has been obtained, the attacker can begin moving toward higher-value systems.
Healthcare Remains a Frequent Target
Although Medusa does not appear to limit itself to a single industry, the Healthcare and Public Health sector has repeatedly appeared among its victims.
That makes healthcare particularly important from a defensive perspective.
Hospitals and healthcare organizations operate complex environments containing clinical systems, identity infrastructure, medical devices, file servers, remote-access technologies, and highly sensitive patient information.
They also face operational pressure that can make ransomware especially disruptive.
A successful attack does not merely threaten confidential information. It can interfere with appointments, diagnostics, administrative services, communications, and other critical operations.
Medusa Uses an Opportunistic Strategy
The updated advisory emphasizes that Medusa actors appear to operate opportunistically rather than exclusively hunting specific organizations or sectors.
In practical terms, that means an organization does not need to be famous, wealthy, or politically significant to become a target.
A vulnerable system may be enough.
This is one of the most important lessons from the campaign: ransomware defense cannot be based solely on assumptions about whether an organization is “interesting” to attackers.
An exposed vulnerability can make an organization interesting very quickly.
Living Off the Land Makes Detection Harder
Medusa also relies heavily on legitimate software and “living off the land” techniques.
Rather than deploying obvious malicious tools immediately, attackers can abuse software already installed within the victim’s environment.
Remote administration utilities, command-line tools, scripting environments, and remote-access services can all become weapons in the hands of an intruder.
This creates a difficult detection problem.
Security teams cannot simply block every legitimate administrative utility because doing so could disrupt normal business operations.
Instead, defenders need to understand who is using a tool, where it is being used, when it is being used, and what behavior surrounds it.
Remote Desktop Protocol Can Become an Attack Highway
The advisory also highlights Remote Desktop Protocol and remote monitoring and management software as potential tools for lateral movement.
Once attackers obtain an initial foothold, they may attempt to move deeper into the network.
The objective is usually not to encrypt the first machine they compromise.
The real prize is broader control.
Attackers may search for privileged credentials, domain administrators, backup systems, file servers, virtualization infrastructure, and other systems that can increase the eventual impact of the ransomware deployment.
Credential Theft Comes Before Destruction
Medusa’s operations can involve credential access before ransomware deployment.
Credentials provide attackers with the ability to impersonate legitimate users, access additional systems, and bypass security controls that depend heavily on passwords.
A stolen administrator account can be substantially more valuable than a single vulnerable workstation.
This is why identity security has become inseparable from ransomware defense.
Strong authentication, privileged-access management, credential monitoring, and segmentation can significantly reduce the damage caused by a compromised account.
Data Theft Is Part of the Extortion Equation
Modern ransomware groups increasingly treat encryption as only one part of the attack.
Before deploying ransomware, attackers may attempt to steal sensitive information.
That creates the possibility of double extortion: victims face both operational disruption from encryption and the threat of confidential information being leaked or sold.
For organizations, this changes the economics of an incident.
Even if backups allow systems to be restored, stolen data can remain outside the organization’s control.
The Victim Count Tells a Larger Story
The increase from more than 300 known victims in March 2025 to more than 500 by April 2026 is one of the clearest indicators of Medusa’s expanding reach.
It also demonstrates why ransomware statistics should not be viewed as isolated numbers.
Every additional victim can represent another exploited vulnerability, another compromised identity, another stolen dataset, another interrupted service, and another organization forced into emergency recovery.
The growth suggests that
Microsoft Has Also Observed Rapid Medusa Operations
Earlier in 2026, Microsoft described activity from a threat group it tracks as Storm-1175, which was observed using Medusa ransomware in rapid attacks.
The reporting adds another layer to the picture: ransomware operations are increasingly optimized for speed.
The faster an attacker can move from initial access to credential theft, lateral movement, data collection, and encryption, the less opportunity defenders have to interrupt the attack.
That makes behavioral detection increasingly important.
North Korean Hackers and Medusa Activity
Research published earlier this year by security companies including Symantec and Carbon Black also described North Korean-linked activity involving Medusa ransomware against healthcare organizations.
This highlights another important development in the ransomware ecosystem: malware families and ransomware brands can sometimes be adopted by different criminal or state-linked actors.
The presence of the same ransomware family across different campaigns does not automatically mean all operators belong to the same organization.
Instead, ransomware-as-a-service models can create overlapping infrastructure, tools, affiliates, and criminal partnerships.
Deep Analysis: How a Medusa-Style Attack Can Unfold
A typical Medusa intrusion can be understood as a sequence of stages rather than a single ransomware event.
1. Initial Access
Attackers may begin by exploiting an internet-facing vulnerability, purchasing access from an initial-access broker, compromising credentials, or abusing remote-access infrastructure.
Defenders should identify externally exposed services continuously.
Useful Linux commands for identifying listening services include:
ss -tulpn
For a basic review of active network connections:
ss -antp
These commands are useful during defensive investigations to understand which services are exposed locally.
2. Patch Verification
Security teams should determine whether critical external applications are running vulnerable versions.
On Debian- or Ubuntu-based systems, administrators can review installed packages with:
dpkg -l
On RPM-based systems:
rpm -qa
The goal is not simply to collect package information, but to compare installed software against trusted vendor advisories and the organization’s vulnerability-management data.
3. Suspicious Process Detection
During an investigation, defenders can inspect running processes with:
ps aux
For a more focused review:
ps aux --sort=-%cpu | head
Unexpected administrative tools, scripts, remote-management processes, or unusual parent-child process relationships deserve investigation.
4. Network Connection Review
A compromised machine may communicate with command-and-control infrastructure or other systems inside the organization.
Defenders can review active connections with:
ss -tunap
Unexpected outbound connections from servers that normally have limited internet access can be particularly valuable investigative signals.
5. Authentication Monitoring
Authentication logs can reveal abnormal access patterns.
On many Linux systems:
journalctl -u ssh
Administrators can also inspect authentication records where available:
last
The objective is to identify unusual login times, unfamiliar source addresses, repeated failures, or unexpected privileged access.
6. Windows Defensive Investigation
On Windows systems, PowerShell can be used to inspect running processes:
Get-Process | Sort-Object CPU -Descending
Active network connections can be reviewed with:
Get-NetTCPConnection
Security teams can also examine recent Windows events through:
Get-WinEvent -LogName Security -MaxEvents 100
These commands are defensive investigation examples and should be used as part of an authorized incident-response process.
7. Protect the Identity Layer
Organizations should enforce phishing-resistant multifactor authentication wherever possible, especially for administrators and remote-access systems.
Privileged accounts should be separated from everyday accounts.
Administrative credentials should not be reused across systems.
8. Segment Critical Infrastructure
Network segmentation can limit the blast radius of a ransomware attack.
Critical servers, backup systems, identity infrastructure, and sensitive databases should not be freely reachable from ordinary workstations.
Segmentation does not guarantee that ransomware will be stopped, but it can make lateral movement considerably more difficult.
9. Protect Backups
Offline or otherwise isolated backups remain one of the most important ransomware defenses.
Backups should be tested regularly.
A backup that has never been successfully restored is not a reliable recovery strategy.
10. Monitor Administrative Tools
Security teams should establish a baseline for remote administration software.
The presence of a legitimate tool is not automatically suspicious.
However, a legitimate tool appearing suddenly on a server, launched by an unusual account, at an unusual time, followed by credential access and network scanning, can become a powerful detection signal.
What Undercode Say:
Ransomware Has Become an Industry
Medusa’s evolution demonstrates that ransomware is no longer simply a collection of hackers writing malicious encryption software.
It is an ecosystem.
Access Has a Price
The reported broker payments show that network access itself has become a commodity.
Attackers can purchase a foothold rather than spending weeks creating one.
Speed Beats Perfection
Medusa does not need to discover every vulnerability.
It needs to exploit known vulnerabilities faster than organizations can patch them.
The First 24 Hours Matter
The
Exposure Is the Real Enemy
An unpatched internet-facing service can become an invitation.
Security teams should continuously identify systems that are reachable from the public internet.
Healthcare Faces Unique Pressure
Healthcare organizations remain attractive because downtime can have immediate operational consequences.
Living Off the Land Is Difficult to Block
Attackers can use tools that administrators already trust.
That makes behavior-based detection more important than simple application blacklists.
Identity Is the New Perimeter
A stolen privileged account can provide attackers with access that bypasses many traditional network defenses.
Ransomware Is Becoming More Modular
Initial-access brokers, ransomware affiliates, data-theft operators, and infrastructure providers can perform different roles.
Criminal Specialization Increases Efficiency
Specialization allows attackers to focus on what they do best while buying services from others.
Vulnerability Management Must Become Faster
Organizations cannot afford patch cycles designed around comfortable schedules when attackers are operating on a 24-hour timeline.
Asset Discovery Comes First
You cannot patch a system you do not know exists.
Shadow IT Creates Risk
Unknown applications and forgotten internet-facing systems can become entry points.
Remote Access Needs Strong Controls
RDP and remote-management platforms should be protected by strong authentication, access restrictions, monitoring, and segmentation.
Detection Must Follow the Attack Chain
Organizations should look for sequences of suspicious behavior rather than individual alerts.
Credential Theft Is a Major Warning Signal
Unusual credential-access activity can be an early indicator that attackers are preparing for lateral movement.
Data Exfiltration Should Trigger Urgency
Unexpected large transfers of sensitive information can indicate that ransomware deployment may be approaching.
Backups Must Be Isolated
Attackers understand that destroying recovery infrastructure can increase pressure on victims.
Zero-Day Development Is Not Required
Medusa’s case demonstrates that attackers can cause enormous damage using vulnerabilities that defenders already know about.
Known Vulnerabilities Remain Dangerous
A vulnerability does not become harmless simply because a patch exists.
Exploitation Is a Race
The relevant question is no longer only whether a vulnerability has been patched.
The question is how quickly it can be patched after exploitation begins.
Security Teams Need Automation
Automated asset discovery, vulnerability prioritization, identity monitoring, and endpoint detection can shorten response times.
Ransomware Defense Is Operational
Policies alone do not stop ransomware.
Continuous monitoring and rapid response do.
Human Visibility Still Matters
Automated alerts need analysts who understand the environment and can distinguish malicious behavior from normal administration.
The Medusa Model Can Be Repeated
Other ransomware groups can adopt similar broker-based and vulnerability-driven strategies.
The Threat Will Not Stay Static
Attackers continuously modify infrastructure and tactics when defenders improve their controls.
Healthcare Is Not the Only Risk
The opportunistic nature of Medusa means organizations across industries can become targets.
Internet Exposure Should Be Minimized
Services that do not need public access should not be publicly accessible.
Security Debt Has a Cost
Old software and forgotten systems can remain dangerous long after their vulnerabilities become widely known.
Incident Response Should Be Practiced
Organizations should rehearse ransomware scenarios before an actual incident occurs.
Recovery Speed Matters
The faster an organization can isolate systems and restore trusted infrastructure, the less leverage attackers possess.
Prevention and Detection Must Work Together
No single control is sufficient against a determined ransomware operator.
The Biggest Lesson Is Time
Medusa’s success is a reminder that cybersecurity increasingly depends on reducing the time between vulnerability disclosure, detection, containment, and remediation.
✅ Victim Count Increased
The updated government advisory reports that known Medusa victims increased from more than 300 in March 2025 to more than 500 by April 2026. This supports the article’s central claim that the operation has expanded.
✅ Access Brokers Are Part of the Ecosystem
The advisory states that Medusa actors use access brokers and describes payments ranging from roughly $100 to $1 million, with higher compensation associated with exclusive access arrangements.
✅ Rapid Exploitation Is Documented
The advisory says Medusa actors have exploited newly announced vulnerabilities within 24 hours and have also been observed using exploits before public vulnerability disclosure.
❌ Medusa Is Not Confirmed to Develop Its Own Zero-Days
The article should not imply that Medusa routinely discovers its own zero-day vulnerabilities. The updated advisory specifically says investigators have no indication that Medusa actors develop their own zero-day or N-day vulnerabilities.
✅ Healthcare Has Been Frequently Targeted
The government advisory identifies the Healthcare and Public Health sector as a frequent victim of Medusa activity, supporting the article’s emphasis on healthcare risk.
✅ Living-Off-the-Land Techniques Are Documented
The advisory states that Medusa actors frequently use legitimate tools and living-off-the-land techniques, as well as remote monitoring, remote-access services, and RDP for lateral movement.
Prediction
(+1) Medusa Will Continue Expanding Through Speed and Criminal Partnerships
Medusa is likely to remain a significant ransomware threat as long as it can combine purchased access, rapid exploitation, credential theft, legitimate administration tools, and data extortion into a repeatable operational model.
The most important change may not be the emergence of a revolutionary new Medusa technique. It may be the continued optimization of existing techniques.
Attackers have already demonstrated that exploiting a newly disclosed vulnerability within a day can put them ahead of traditional enterprise patch cycles.
That advantage could become even more significant as vulnerability exploitation becomes increasingly automated.
Organizations that rely on monthly or manually coordinated remediation processes may therefore face increasing pressure to accelerate their response.
At the same time, stronger identity security, network segmentation, endpoint detection, attack-surface management, and resilient backups can substantially reduce the impact of a successful intrusion.
The future of ransomware defense will increasingly be determined by one factor: who can move faster—the attacker or the defender?
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