Incident Response Playbook for DDoS Attack Handling (Updated 2025)

This Distributed Denial-of-Service (DDoS) Incident Response Playbook provides a structured approach to detecting, mitigating, remediating, and recovering from DDoS attacks. Modern updates include advanced network monitoring, collaboration with ISPs and anti-DDoS service providers, and integration with traffic analysis tools.

1. Preparation

Objective: Establish protocols, contacts, and infrastructure to reduce response times and mitigate the impact of potential DDoS attacks.

Key Steps:

1. ISP and Anti-DDoS Services:

   • Contact your Internet Service Provider (ISP) to understand available DDoS mitigation services, including both free and paid options.

   • Subscribe to redundant Internet connections or an anti-DDoS solution.

   • Ensure 24/7 support availability from your ISP and mitigation providers.

2. Network and Infrastructure Setup:

   • Design a network infrastructure with no single point of failure.

   • Implement Web Application Firewalls (WAFs) to protect critical services from application-layer DDoS attacks.

   • Distribute DNS servers and other essential services (e.g., email servers) across multiple autonomous systems (AS).

   • Harden OS, network, and application configurations against common DDoS techniques.

3. Documentation:

   • Maintain a list of critical IP addresses, protocols, and business partners for prioritising traffic during attacks.

   • Create and regularly update network topology diagrams and asset inventories.

4. Baseline Performance:

   • Establish baseline performance metrics to quickly detect deviations caused by a DDoS attack.

   • Set DNS time-to-live (TTL) values for flexible redirection in case of attack.

5. Internal Contacts:

   • Define roles for response teams, including SOC analysts, network administrators, and business continuity planners.

   • Establish secure out-of-band communication channels.

2. Identification

Objective: Detect the attack, assess its scope, and engage appropriate stakeholders.

Steps:

1. Communication Plan:

   • Prepare internal and external communication templates for DDoS incidents.

   • Identify where and how information will be distributed (e.g., emails, dashboards, public notices).

2. Analyse the Attack:

   • Check traffic reports from anti-DDoS services and scrubbing centres.

   • Determine whether your organisation is the primary target or a collateral victim.

   • Use network analysis tools (e.g., tcpdump, Wireshark, Snort) to inspect DDoS traffic for patterns such as:

     • Source IPs and AS numbers.

     • Targeted protocols and destination ports.

     • Abnormal URLs or flags in packet headers.

3. Gather Background Information:

   • Investigate whether the attack is part of a larger threat campaign, possibly tied to extortion attempts or hacktivist groups.

   • Search security email logs and public channels (e.g., social media) for related threat actor activity.

4. Notify Stakeholders:

   • Inform executive leadership, legal teams, and law enforcement if necessary.

   • Contact your ISP with specific information about the attack (e.g., network blocks, malicious IP addresses).

3. Containment

Objective: Mitigate the effects of the DDoS attack and maintain service availability.

Steps:

1. Throttling and Blocking:

   • Apply rate limiting and filtering rules on routers, firewalls, or load balancers to block malicious traffic.

   • If application-layer services are overwhelmed, temporarily disable resource-intensive features.

2. Traffic Redirection:

   • Use DNS or routing changes to redirect traffic to a scrubbing centre or traffic sinkhole.

   • Consider switching services to alternate network locations if available.

3. Terminate Malicious Connections:

   • Identify and terminate unwanted TCP/UDP connections on servers.

   • Adjust server TCP/IP stack settings to reduce susceptibility to SYN floods or similar attacks.

4. Customer Communication:

   • Set up alternate communication channels (e.g., status update pages, voice servers) to inform customers and stakeholders about service disruptions.

4. Remediation

Objective: Stop the denial-of-service condition and secure the network.

Steps:

1. Collaborate with ISP:

   • Work with your ISP or anti-DDoS provider to implement remediation measures, such as:

     • Traffic filtering at upstream routers.

     • Traffic scrubbing to remove malicious packets before they reach your network.

     • IP address switching to avoid targeted addresses.

2. Monitor Traffic:

   • Use real-time network monitoring tools to assess the effectiveness of mitigation efforts.

   • Ensure that all attack vectors (e.g., DNS amplification, HTTP floods) are addressed.

3. Compliance and Reporting:

   • If the attack has regulatory implications, prepare an incident report for submission to authorities.

   • Collaborate with legal teams to determine whether law enforcement should be involved.

5. Recovery

Objective: Restore services to normal operations and verify infrastructure stability.

Steps:

1. Assess Recovery:

   • Confirm that affected services are fully reachable and that performance matches baseline levels.

   • Validate that critical business functions have resumed without errors.

2. Rollback Temporary Measures:

   • Gradually re-enable previously disabled services and revert DNS or routing changes.

   • Monitor closely for any signs of reinfection or recurring attacks.

3. Coordinate with Teams:

   • Ensure network and application teams are aware of service restarts to prevent cascading failures.

6. Lessons Learned

Objective: Document the incident, evaluate response performance, and improve future readiness.

Steps:

1. Incident Report:

   • Compile a detailed report covering:

     • Initial detection and response timelines.

     • Attack vectors, sources, and impact.

     • Actions taken and their outcomes.

2. Evaluate Performance:

   • Identify what went well and areas for improvement.

   • Review the effectiveness of mitigation tools and partnerships (e.g., ISP services).

3. Implement Improvements:

   • Update incident response playbooks with lessons learned.

   • Strengthen DDoS defences, including additional infrastructure hardening, improved monitoring, and updated traffic filtering rules.

4. Training and Awareness:

   • Conduct training sessions to ensure that staff understand new procedures and tools.

   • Simulate DDoS scenarios to test and validate response readiness.

Conclusion

This DDoS Incident Response Playbook equips organisations with a comprehensive plan to detect, contain, mitigate, and recover from DDoS attacks. Regular testing and updates to the playbook will ensure continued resilience against evolving DDoS threats.

For additional resources, including communication templates, traffic analysis scripts, and tool recommendations, please contact our cybersecurity support team.