What is a DDoS Attack?
A distributed denial-of-service (DDoS) attack is a cyberattack where multiple compromised computers flood a target system, server, or network with excess traffic. The goal is to exhaust resources and make the targeted services unavailable to legitimate users.
Attackers deploy botnets, networks of infected devices, to amplify the scale of these assaults and make mitigation difficult. DDoS attacks can cause minutes to days of disruption, depending on their size and the target’s defensive capabilities.
The motives behind DDoS attacks range from seeking ransom and retaliation to activism or simple disruption. Attackers leverage different vectors such as volumetric methods, protocol exploitation, or application-layer abuse based on the weaknesses of the target.
Healthcare organizations, with their public-facing portals, legacy systems, and need for continuous uptime, are particularly vulnerable. Unlike traditional breaches that focus on data theft, DDoS attacks mainly focus on paralyzing operations by overwhelming digital infrastructure.
In this article:
Healthcare organizations depend on continuous access to digital systems for patient care, diagnostics, and real-time decision-making:
- Operational urgency: Even short outages can disrupt critical services, delay treatment, and endanger lives. This makes healthcare networks particularly vulnerable to DDoS extortion attempts, as organizations may be more likely to pay ransoms to restore service quickly.
- Outdated systems: In addition to their dependency on uptime, healthcare networks often include legacy systems and poorly segmented infrastructure, making them easier to overwhelm or exploit. Many organizations struggle to maintain updated defenses due to budget constraints or complex compliance requirements.
- Value of healthcare data: While DDoS attacks don't steal data directly, they can serve as a diversion for parallel intrusions. During an outage, security teams are often distracted, creating a window for data theft or lateral movement within the network.
- Critical infrastructure: Attacks on hospitals and providers may be politically or ideologically motivated, targeting public trust or aiming to create large-scale disruption with limited effort.
Volumetric Attacks on Patient Portals and Public-Facing Services
Volumetric attacks overwhelm internet-facing resources by saturating bandwidth with high volumes of traffic. Patient portals, telehealth platforms, and public web services are particularly susceptible because they are accessible from outside the organization. Attackers use reflection and amplification techniques to increase the impact, often employing protocols like DNS or NTP to boost attack volume.
These attacks disrupt routine operations, prevent appointment scheduling, and inhibit communication between patients and healthcare providers. In emergency scenarios, outages can delay care coordination, leaving patients without medical attention. Health organizations frequently face significant reputational harm as users lose confidence in their reliability.
Protocol Attacks Against Network and VPN Infrastructure
Protocol attacks exploit weaknesses in network protocols to consume server and network device resources. Common vectors include SYN floods, fragmented packet attacks, and exploitation of internet control message protocol (ICMP) vulnerabilities. Healthcare networks are often interconnected via VPNs for secure staff access to internal resources.
An attack on VPN gateways can sever connections for remote clinicians, impeding access to clinical applications and sensitive data when it is needed most. These attacks are challenging because they use packets that appear legitimate, making detection and filtering more difficult than with volume-based assaults. Access to healthcare applications like electronic health records (EHRs) or imaging repositories may be disrupted.
Application-Layer Attacks Targeting EHR, PACS, and APIs
Application-layer attacks focus on disrupting specific applications or services by overwhelming them with seemingly valid, resource-intensive requests. EHR systems, picture archiving and communication systems (PACS), and healthcare APIs are frequent targets. Attackers may automate login attempts, search queries, or API calls to strain server resources, crash backend databases, or lock legitimate users out of accounts.
Related content: Read our guide to DDoS types.
Because these attacks mimic normal user behavior, identifying and mitigating them is more complex. Healthcare APIs expose fragile interconnections across organizations and third-party partners, so targeted attacks here can have ripple effects throughout the ecosystem. The result can be delayed diagnostics, halted clinical workflows, and interrupted communication with labs or pharmacies.
Eva Abergel
Eva Abergel is a solution expert in Radware’s security group. Her domain of expertise is DDoS protection, where she leads positioning, messaging and product launches. Prior to joining Radware, Eva led a Product Marketing and Sales Enablement team at a global robotics company acquired by Bosch and worked as an Engineer at Intel. Eva holds a B.Sc. degree in Mechatronics Engineering from Ariel University and an Entrepreneurship Development certificate from the York Entrepreneurship Development Institute of Canada.
Tips from the Expert:
In my experience, here are tips that can help you better defend healthcare organizations from DDoS attacks:
Deploy geo-fencing and reputation-based filtering: Many healthcare DDoS attacks originate from regions with no operational ties to the organization. Use geo-fencing and IP reputation services to proactively block or throttle traffic from non-essential geographies and known malicious IP ranges, reducing attack surface at the perimeter.
Rate-limit unauthenticated traffic to critical portals: Implement smart rate-limiting policies that specifically throttle unauthenticated or anonymous traffic to patient portals, scheduling systems, and telehealth entry points. Legitimate users can be prioritized via token-based authentication or CAPTCHA validation, reducing resource strain during attacks.
Use service mesh controls to limit internal DDoS blast radius: Leverage service mesh architectures (e.g., Istio, Linkerd) to apply fine-grained traffic control between microservices. This limits how a targeted API or application-layer attack on one component affects other critical services like EHRs or PACS.
Integrate DDoS telemetry with clinical risk dashboards: Correlate DDoS-related service degradations with clinical risk scoring dashboards used in hospitals. This enables operational leads to make informed decisions (e.g., diverting ambulances or activating manual fallback protocols) based on real-time IT risk conditions.
Harden VPN and remote access pathways using behavioral analytics: Use UEBA (User and Entity Behavior Analytics) to monitor for unusual session patterns or traffic bursts in VPN connections. Protocol-based DDoS attacks against VPNs can mask brute-force or insider misuse, especially in hybrid workforce environments.
Disruption of Critical Patient Care Systems and Portals
DDoS attacks can take down vital healthcare portals, scheduling tools, and communication systems, making it impossible for staff and patients to interact online. Patient portals that enable prescription refills, appointment bookings, and direct messaging between patients and physicians are often among the first targets.
When these services are offline, administrative bottlenecks build up quickly, forcing providers to revert to inefficient manual processes or cancel patient interactions entirely. Such disruptions extend beyond front-facing tools. Internal clinical applications vital for managing daily workflows, such as lab ordering, radiology scheduling, or telehealth platforms, are equally affected.
Risk to Patient Safety Due to Lack of Access to Records or Systems
Patient safety is directly threatened when DDoS attacks cripple access to EHRs or supporting clinical information systems. Physicians and nurses may be unable to retrieve vital patient histories, allergy lists, medications, or diagnostic images during critical windows of care. In emergency rooms or intensive care units, even brief interruptions can escalate clinical risks, delay urgent interventions, or lead to medical errors.
Downtime may force caregivers to adopt paper-based or ad hoc workarounds, heightening the chance of incomplete documentation or manual entry mistakes. Lost or inaccessible records impede transitions of care and follow-up, eroding quality standards and compliance with patient safety regulations.
Financial Costs of Mitigation, Downtime, and Recovery
The financial impact of DDoS attacks on healthcare is substantial. Organizations incur direct costs associated with incident response, emergency IT support, and investment in new mitigation tools or cloud services. There are also indirect losses such as reduced patient volumes, canceled procedures, and overtime for staff managing the aftermath.
Some healthcare providers may face contractual penalties or suffer increased audit scrutiny due to compliance lapses triggered by prolonged outages. Recovery extends far beyond restoring technical service. Organizations must conduct thorough forensic reviews, strengthen vulnerable systems, and often provide public communication to rebuild trust.
Here are some of the ways that healthcare organizations can better protect themselves against denial of service attacks.
1. Implement Always-On DDoS Monitoring
Continuous DDoS monitoring establishes a baseline for network traffic and enables rapid identification of abnormal patterns. By maintaining vigilance around the clock, healthcare organizations can spot DDoS attack signs early, often before full-scale outages develop. Always-on monitoring tools leverage machine learning and threat intelligence feeds to distinguish between legitimate spikes and malicious surges in traffic.
These systems provide security teams with actionable alerts and detailed diagnostics. This enables rapid triage and targeted response, preserving system availability for mission-critical clinical applications. Continuous monitoring also supplies valuable log data for post-incident forensics, ensuring that organizations can refine defenses against evolving attack techniques.
2. Maintain Accurate Network and Application Inventories
An up-to-date inventory of all networked assets is critical to DDoS defense. Healthcare organizations must know what public-facing services, APIs, and internal applications exist to protect them effectively. Inventories should include communication tools, IoT-enabled medical devices, and cloud-based resources as well as traditional infrastructure.
This clarity helps security teams map attack surfaces, prioritize risk assessments, and simplify deployment of mitigation technologies. Clear asset visibility also allows for proactive patching, secure configuration, and the identification of orphaned or unnecessary services that may expose additional risk. During an attack, knowledge of the environment’s topology aids in quickly pinpointing points of failure or likely targets.
3. Segment Clinical, Administrative, and Public Traffic
Network segmentation separates sensitive clinical systems from public or administrative traffic, isolating vital operations in the event of an attack. By compartmentalizing networks and restricting lateral movement, organizations make it harder for attackers to disrupt all services at once. Segmentation policies ensure that critical EHR, imaging, or diagnostic platforms remain accessible to trusted staff even if patient portals or external-facing APIs are under siege.
Implementation requires detailed mapping of workflows and traffic flows to avoid unintended bottlenecks that could impede care. Segmented architectures also support tailored security controls and monitoring at each network boundary, improving detection and containment efficiency for attacks.
4. Establish DDoS-Specific Incident Response Playbooks
A well-crafted, DDoS-specific incident response playbook outlines step-by-step actions to take during various types of attacks. Playbooks should detail roles and responsibilities, escalation paths, internal and external communications strategies, and engagement protocols with technology vendors and ISPs. These pre-planned workflows support rapid, coordinated responses, minimizing confusion and delays when every second counts.
Regular tabletop exercises and simulations help keep playbooks current and familiar to all stakeholders. Post-incident reviews and lessons learned should drive continuous improvement of these procedures. The existence of a DDoS-specific playbook ensures regulatory compliance, reduces legal liability, and reassures leadership that the organization is prepared.
5. Coordinate with ISPs and Upstream Providers
Establishing clear lines of communication with internet service providers (ISPs) and hosting partners strengthens an organization’s DDoS resilience. ISPs have the capability to filter or block malicious traffic upstream, reducing the load on on-premises infrastructure before it reaches the network edge. Early warning systems provided by upstream partners can deliver timely notifications about abnormal traffic or attack activity directed at healthcare systems.
Coordination should include prearranged contact methods, escalation procedures, and participation in joint incident response drills. Legal agreements with providers may also stipulate levels of support during major incidents. Collaborating with ISPs and upstream services transforms DDoS defense from a purely internal effort into a shared responsibility.
6. Regularly Test Failover and Redundancy Mechanisms
Routine testing of technical failover and redundancy systems is crucial to verify the organization’s ability to maintain essential operations under DDoS conditions. These mechanisms might include secondary data centers, backup network connections, or cloud-based load balancing services.
Simulation exercises should mimic real attack conditions to confirm that systems automatically redirect traffic or activate backup resources seamlessly when thresholds are breached. Frequent tests also reveal misconfigurations, licensing gaps, or hardware problems before they manifest during a real incident. Documentation of these tests is valuable for regulatory audits and insurance claims.
Healthcare organizations require continuous protection against volumetric, protocol, and application-layer DDoS attacks that can disrupt patient portals, VPN access, telehealth services, and clinical systems.
Radware DefensePro provides inline, behavior-based DDoS mitigation that detects and blocks abnormal traffic patterns in real time, protecting VPN gateways, internal healthcare applications, and network infrastructure before service degradation occurs.
For large-scale or multi-vector campaigns, Radware Cloud DDoS Protection Service delivers upstream scrubbing to absorb attack traffic before it reaches hospital networks, helping maintain availability of public-facing and patient-access systems during sustained attacks.
Radware Cloud Application Protection Service secures web applications and APIs with integrated WAF, API protection, bot mitigation, and application-layer DDoS defenses, protecting EHR portals and healthcare APIs from targeted floods and automated abuse.
Threat Intelligence Subscriptions further strengthen defenses by proactively blocking known malicious sources associated with botnets and coordinated attack campaigns.
Together, these layered controls help healthcare organizations implement always-on monitoring, traffic segmentation, incident response readiness, and upstream coordination, ensuring critical systems remain available even under attack.