DDoS Attack 101: Definition, Techniques, Risks & Prevention

A distributed denial-of-service (DDoS) attack occurs when multiple compromised systems coordinate to flood a target’s network, servers, or applications with malicious traffic, exhausting system resources and preventing legitimate users from accessing services.

Key takeaways:

• DDoS attacks threaten service availability by overwhelming systems with malicious traffic. 
• Modern attacks combine multiple vectors and leverage Internet of Things (IoT) botnets. 
• Effective defense requires layered protection and rapid response capabilities.
• Prevention strategies must evolve with constantly emerging threats.

What is a DDoS attack?

Imagine a restaurant’s reservation system inundated with thousands of fake bookings from different phone numbers. The staff would become so overwhelmed with phony requests that legitimate customers couldn’t reserve tables or place orders. Similarly, in a DDoS attack, cybercriminals use botnets, networks of compromised devices, to send a massive volume of fake requests, paralyzing a target system and preventing real users from accessing it.

The IoT threat

The well-known Mirai botnet attack demonstrated how vulnerable IoT devices can become powerful weapons in DDoS attacks. In this case, hundreds of thousands of devices were compromised by default credentials and simple brute-force attacks. 

Vulnerable devices:

• Security cameras and DVRs 
• Home routers and modems 
• Smart home devices (thermostats, doorbells, voice assistants) 
• Network-attached storage (NAS) devices 
• Printers and print servers 

Critical security weaknesses: 

• Default or hardcoded credentials 
• Lack of automatic security updates 
• Insecure network protocols 
• Poor encryption implementation

It’s not always easy to spot a DDoS attack in progress. And once hackers launch it, cleaning up the damage is difficult. Investing in prevention can lower your risk.

Understanding DDoS attack mechanisms

Infected devices often continue functioning, so users may never know about the problem. And cleaning up an infected device is difficult, especially if users never think to update software or download security patches.

Spotting bots can also be challenging for network administrators. Each one has a separate IP address and looks legitimate. When a problem strikes, it’s hard to know where it originates. 

Evolution of modern DDoS attacks

• Attack Sophistication
  • AI-powered attacks that adapt to defense mechanisms in real-time
  • Multi-vector attacks combining application, protocol, and volumetric methods
  • Advanced evasion techniques mimicking legitimate user behavior
  • Attacks targeting zero-day vulnerabilities in protocols and applications
     
• Infrastructure Changes
  • Cloud service exploitation using legitimate platforms
  • API-focused attacks targeting microservice architectures
  • Edge network manipulation through CDN vulnerabilities
  • Serverless function abuse for distributed attacks
     
• Botnet Evolution
  • IoT device exploitation at a monumental scale
  • Mobile device compromise through malicious apps
  • Cloud-hosted botnet infrastructure
  • Automated botnet coordination using AI/ML
     
• Defense Evasion
  • Dynamic traffic pattern generation
  • Legitimate traffic mixing to avoid detection
  • Geographic distribution to bypass regional blocks
  • Protocol mutation to evade signature detection

How does a DDoS attack work?

Every internet-connected system is subject to resource limitations — from processing power to memory and network capacity. DDoS attacks exploit these limits by flooding systems with more requests than they can handle.

Three main types of DDoS attacks (by OSI layer)

Modern DDoS attacks target different layers of the network stack:

1. Volumetric attacks (layer 3/4)

   • Overwhelm network capacity through massive traffic volumes
   • Examples: DNS amplification, NTP reflection
   • Common indicators: Bandwidth saturation, geographic anomalies
      

2. Protocol attacks (layer 4/5)

   • Exploit network protocol weaknesses
   • Examples: SYN floods, ICMP floods, SSL/TLS attacks
   • Common indicators: High volumes of incomplete connections
      

3. Application layer attacks (layer 7)

   • Target web applications and services
   • Examples: HTTP floods, API abuse, Slowloris
   • Common indicators: High resource utilization on specific endpoints

Examples of notable DDoS attacks by type

Named DDoS vectors by category include:

Application layer attacks

• Slowloris: A precision attack using minimal bandwidth that holds connections open by sending partial HTTP requests
• RUDY (R-U-Dead-Yet): Exploits form fields by submitting data extremely slowly, keeping connections active until server resources are exhausted
• HTTP Slow Read: Maintains many connections by reading responses very slowly, depleting the server’s connection pool

Protocol attacks

• SACK panic: Exploits TCP selective acknowledgment (SACK) to trigger kernel panics in Linux systems
• TCP reset: Abuses TCP by sending spoofed RST packets to terminate legitimate connections
• Ping of Death: Sends malformed ICMP packets that crash systems when reassembled
• Christmas tree attack: Sets all flags in TCP packets, consuming extra processing power for each packet

Volumetric attacks

• Memcached amplification: Exploits misconfigured memcached servers to achieve amplification factors up to 51,000x
• DrDoS (Distributed Reflection DoS): Uses legitimate servers as amplifiers by spoofing a victim’s IP address
• NTP amplification: Exploits Network Time Protocol servers to generate large responses to small requests
• CLDAP reflection: Abuses Connection-less LDAP to achieve amplification factors around 56x

Advanced/hybrid attacks

• Carpet bombing: Targets multiple IP addresses in the same network range simultaneously
• Advanced persistent DoS (APDoS): Combines multiple attack vectors with persistence mechanisms to maintain long-term pressure
• Pulse wave: Alternates between high-volume attack bursts and quiet periods to bypass mitigation
• Multi-vector: Combines multiple attack types simultaneously, often switching vectors to evade defense

DDoS attack response and mitigation

When systems are under attack, time is of the essence. Here’s how organizations can act effectively:

Immediate actions

• Traffic analysis: Identify attack patterns and measure traffic volumes and types
• Communication: Notify internal IT teams, service providers, and stakeholders
• Action planning: Establish clear priorities and delegate tasks to team members

Active mitigation strategies

• Activate traffic scrubbing: Deploy third-party providers or in-house scrubbing tools to filter malicious traffic
• Implement filtering rules: Set up firewalls and intrusion prevention systems (IPS) to block identified attack patterns
• Scale resources: Expand server capacity using cloud resources to absorb volumetric attacks

Proven mitigation techniques

• Blackhole filtering: Discard malicious network traffic at the routing level before it reaches protected systems
• Traffic scrubbing: Remove malicious requests while preserving legitimate traffic using specialized tools or services
• Load distribution: Spread traffic across multiple servers using content delivery networks (CDNs) or load balancers
• Signature adaptation: Real-time modification of detection rules using tools like Snort or Suricata to keep up with changing attack patterns
• ML for traffic analysis: Use anomaly detection models to identify emerging threats and reduce reliance on static rules
• Response automation: Integrate automation tools with existing security infrastructure

Identity layer protection

• Identity infrastructure serves as a critical gateway to digital resources. Maintaining authentication service availability is essential during a DDoS attack. If users can’t authenticate, they can’t access systems, even if those systems are operational. By protecting Identity services with the same robust DDoS mitigation strategies used for an organization’s network infrastructure, attackers are prevented from exploiting this single point of failure.

   

DDoS attack prevention best practices

Preventing DDoS attacks involves a layered approach to defense.

Core protection mechanisms

• Rate limiting: Advanced traffic control systems that dynamically adjust request frequencies based on source behavior and historical patterns
  (e.g., API rate control)
• Web application firewall (WAF): Intelligent filtering of application-layer traffic using behavior-based analysis
• Protocol validation: Deep packet inspection to ensure legitimate connection attempts and protocol conformance

Advanced network architecture defenses

1. Anycast network architecture
   • Distributes traffic across multiple global locations
   • Inherently resistant to volumetric attacks
   • Provides automatic failover capabilities
      
2. BGP flowspec 
   • Enables dynamic routing policy distribution
   • Allows rapid response to attack traffic
   • Provides granular traffic control at the network edge
      
3. Hybrid protection
   • Combines on-premise and cloud-based defenses 
   • Provides defense-in-depth against multi-vector attacks 
   • Enables flexible response to varying attack types

Modern defense architecture

In addition to core defense mechanisms, DDoS protection requires:
 

• Multi-layer traffic analysis: Simultaneous monitoring across network layers for comprehensive visibility
• Cloud-native scrubbing services: Leverage distributed scrubbing centers to mitigate geographically dispersed attacks
• Automated response systems: Incorporate security information and event management (SIEM) platforms for centralized, automated mitigation
• Machine learning pattern recognition: Identify and counter emerging threats with adaptive algorithms
• Advanced rate-limiting techniques: Implement adaptive thresholds to respond dynamically during attack scenarios

Industry-specific DDoS protection

Different sectors require specific protection strategies based on their unique vulnerabilities and requirements.

Regulatory compliance for DDoS protection

SEC requirements

• Major incident reporting: Report significant DDoS attacks that disrupt operations or services
• Documentation: Maintain records of DDoS mitigation controls and response procedures
• Regular updates: Keep disclosure documentation current as the threat landscape changes

GDPR considerations

• Service availability: Protect against disruptions to data access
• Technical controls: Implement appropriate DDoS prevention measures
• Financial impact: Organizations face penalties for failing to prevent service disruptions

Critical infrastructure protection

• Sector rules: Different industries have unique DDoS protection requirements
• CISA compliance: US operators must follow specific mitigation protocols
• EU NIS2 standards: European providers need baseline security measures in place

Cross-border data requirements

• Location restrictions: DDoS mitigation strategies must respect data residency rules
• Vendor selection: Choose scrubbing services with compliant data center locations
• Data routing: Monitor traffic routing during DDoS mitigation

Current trends and future outlook

DDoS attacks are evolving with more sophisticated techniques:

• AI-enhanced attacks: Advanced pattern generation and automated target selection
• IoT security challenges: Exploiting vulnerabilities in connected devices for botnet creation
• Advanced protection: Implementing machine learning, behavioral analysis, and predictive DDoS defense strategies to counter evolving threats

Frequently asked questions about DDoS attacks

Q: How can I tell if I’m under a DDoS attack?

A: Fundamental indicators of a DDoS attack include sudden traffic spikes, service slowdowns, and unusual patterns in server logs. Organizations should monitor geographic sources, request rates, and resource usage for early warning signs.

Q: What’s the difference between DoS and DDoS Attacks?
A: A DoS attack comes from one source attempting to flood a target with traffic or resource-consuming requests. The attack is often from one or a few computers where a bad actor aims to render a target unavailable or deny user access to services or assets. A DDoS attack generally occurs when many compromised computers or devices form a botnet and launch a coordinated attack effort. By directing botnets to flood traffic or requests to a target system simultaneously, distributed attacks are more difficult to defend against.  

Q: What is an IoT device attack?

A: An IoT device attack is a malicious attempt to exploit vulnerabilities in an internet-connected device. By exploiting weaknesses in device security protocols or firmware, bad actors can co-opt everything from smart home appliances to medical devices and industrial control systems to gain unauthorized access, misappropriate sensitive data, or use the device as part of a larger cyber attack, such as a botnet during a DDoS attack.

Q. How long does a DDoS attack last?

A. Typically, DDoS attacks last less than 10 minutes, but without proper protection, DDoS attacks can range from minutes to days.

Take action to protect against DDoS attacks with Okta

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