On Tuesday 3 August 2021 at 17:17 UTC, a cache-busting query flood targeted a fashion retail customer in North America. The attack peaked at 737.0 million requests per second and lasted 161 minutes. Traffic originated from 2741 autonomous systems in 114 countries, predominantly a rented booter service.
| Vector | cache-busting query flood |
| Peak | 737.0 million requests per second |
| Duration | 161 min |
| Time to mitigation | 0.902 s |
| Attack traffic reaching origin | 0.007% |
| Legitimate traffic challenged | 0.70% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 244 within 7 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.
What the customer saw
A brief increase in p99 latency of 27 ms during the first minute, then normal service.
Recommendations
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Keep origin IPs out of public DNS history.
- Enable authenticated origin pulls.
Thanks — sharing this with our on-call team.
Great to hear, thanks for sharing your experience.
Clear and practical, thanks.
Good question. We will cover that in a follow-up post.