An HTTP flood attack is a type of application-layer denial-of-service attack that overwhelms a website, application, or API with large volumes of HTTP or HTTPS requests. By forcing servers to process excessive requests, attackers consume application resources and degrade performance, making services slow, unreliable, or completely unavailable to legitimate users.

Unlike volumetric attacks that target network bandwidth, HTTP flood attacks focus on exhausting application resources, making them more difficult to distinguish from legitimate user traffic.

{{anchor:Overivew}}

How HTTP flood attacks work

HTTP flood attacks generate large numbers of seemingly valid requests that mimic normal user behavior.

Common attack techniques include:

• Excessive HTTP get requests
• High-volume HTTP post requests
• Requests targeting resource-intensive application functions
• Encrypted HTTPS traffic designed to evade inspection
• Automated botnet-generated traffic from distributed sources

Because these requests often appear legitimate, traditional network security controls may struggle to differentiate attack traffic from normal user activity.

{{anchor:Why it matters}}

Why HTTP flood attacks matter

HTTP flood attacks can significantly impact customer-facing applications and business operations.

Potential consequences include:

• Website and application outages
• Degraded performance and slow response times
• Lost revenue and interrupted transactions
• Reduced customer satisfaction
• Increased operational and support costs
• Reputational damage

Organizations that rely on web applications, APIs, e-commerce platforms, financial services, or digital customer experiences are particularly vulnerable to the business impact of these attacks.

{{anchor:Prevention}}

Reducing HTTP flood risks

Organizations can improve resilience against HTTP flood attacks through a layered security approach that includes:

• Traffic monitoring and anomaly detection
• Request rate limiting
• Application performance monitoring
• Scalable infrastructure and content delivery networks (CDNs)
• DDoS mitigation capabilities
• Redundant and resilient DNS architecture
• Regular testing of incident response procedures

Early visibility into abnormal traffic patterns can help organizations identify and respond to attacks before they significantly impact service availability.

{{anchor:How DigiCert helps}}

How DigiCert can help

DigiCert UltraDNS provides a resilient, enterprise-grade DNS foundation that helps organizations maintain the availability and performance of critical digital services. Built on a globally distributed Anycast architecture, UltraDNS helps distribute traffic efficiently, reduce single points of failure, and support business continuity during periods of elevated traffic and attack activity.