On Thursday 11 November 2021 at 16:16 UTC, a WebSocket connection flood targeted a airline booking customer in Western Europe. The attack peaked at 452.4 million requests per second and lasted 81 minutes. Traffic originated from 4041 autonomous systems in 55 countries, predominantly misconfigured open reflectors.
| Vector | WebSocket connection flood |
| Peak | 452.4 million requests per second |
| Duration | 81 min |
| Time to mitigation | 0.485 s |
| Attack traffic reaching origin | 0.062% |
| Legitimate traffic challenged | 0.11% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 627 within 30 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
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Enable authenticated origin pulls.
- Keep origin IPs out of public DNS history.
- Add a dedicated rate limit for the targeted route.
Nice to read a vendor blog that admits what went wrong.
Verified good bots and allow-listed partners bypass challenges entirely.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
Could you share the dataset behind the percentages?
Great to hear, thanks for sharing your experience.
Our auditors asked for exactly this kind of incident evidence under DORA.
Clear and practical, thanks.
Do you publish the edge IP ranges in a machine-readable format?
Nice to read a vendor blog that admits what went wrong.