A distributed denial of service (DDoS) attack is a cyberattack designed to disrupt the availability of a website, application, API, network, or online service by overwhelming it with malicious traffic. By exhausting bandwidth, computing resources, or application capacity, attackers prevent legitimate users from accessing critical services.

DDoS attacks remain one of the most common threats facing organizations today. They can cause service outages, degrade performance, disrupt customer experiences, and create operational challenges that impact revenue, reputation, and business continuity.

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How DDoS attacks work

Most DDoS attacks are launched using a botnet—a network of compromised devices controlled by an attacker. These devices generate large volumes of malicious traffic that are directed at a target simultaneously.

Attackers use a variety of techniques, including:

• Volumetric attacks that consume available bandwidth
• Protocol attacks that exhaust network or server resources
• Application-layer attacks that target web applications and APIs
• Amplification attacks that leverage third-party services to increase attack volume
• Multi-vector attacks that combine several techniques simultaneously

Modern DDoS attacks can range from short, disruptive bursts to sustained campaigns designed to overwhelm defenses and exhaust security teams.

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Why DDoS attacks matter

The impact of a successful DDoS attack extends beyond downtime.

Organizations may experience:

• Service outages and degraded application performance
• Lost revenue and interrupted business operations
• Reduced customer trust and brand reputation damage
• Increased operational and remediation costs
• Distraction of security and IT teams from other critical threats

In some cases, DDoS attacks are used as a diversion while attackers attempt additional activities such as ransomware deployment, credential theft, or data breaches.

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Reducing DDoS risk

While organizations cannot prevent attackers from launching DDoS attacks, they can significantly reduce their impact through preparation and resilience.

Key best practices include:

• Protecting all internet-facing applications, APIs, and networks
• Implementing dedicated DDoS mitigation services
• Continuously monitoring traffic and application performance
• Testing incident response and mitigation procedures
• Maintaining visibility across cloud, hybrid, and on-premises environments
• Leveraging resilient DNS infrastructure and redundant architectures

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How DigiCert can help

DigiCert UltraDNS delivers highly available, authoritative DNS infrastructure built for resilience and performance. With global redundancy, DNSSEC support, and integrated DDoS protections, UltraDNS helps ensure critical online services remain accessible even during attack conditions.