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Interview Question
Your DNS servers are overloaded with suspicious traffic patterns resembling amplification. How do you detect, mitigate, and protect?
Key Points to Cover
- Identify traffic patterns and QPS spikes via logs/metrics
- Confirm reflection/amplification from open resolvers
- Rate-limit or block malicious sources at firewall/CDN
- Engage provider DDoS mitigation services
- Harden DNS infra: anycast, caching, restrict recursion
Evaluation Rubric
Detects attack via DNS metrics/logs30% weight
Applies rate limits or DDoS controls30% weight
Uses provider mitigation effectively20% weight
Mentions long-term DNS hardening20% weight
Hints
- 💡Look for large response-to-query ratios.
Common Pitfalls to Avoid
- ⚠️Failing to distinguish between legitimate traffic spikes and amplification patterns.
- ⚠️Assuming all UDP traffic on port 53 is malicious without verification.
- ⚠️Not implementing rate limiting or access controls effectively at the network edge or firewall.
- ⚠️Neglecting to harden DNS server configurations to prevent open recursion.
- ⚠️Focusing solely on immediate mitigation without planning for long-term resilience and prevention.
Potential Follow-up Questions
- ❓How to configure response rate limiting?
- ❓How to test DDoS readiness?
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