On Friday 6 May 2022 at 04:21 UTC, a WebSocket connection flood targeted a healthcare portal customer in the Benelux. The attack peaked at 974.8 million requests per second and lasted 29 minutes. Traffic originated from 3353 autonomous systems in 59 countries, predominantly misconfigured open reflectors.
| Vector | WebSocket connection flood |
| Peak | 974.8 million requests per second |
| Duration | 29 min |
| Time to mitigation | 0.558 s |
| Attack traffic reaching origin | 0.075% |
| Legitimate traffic challenged | 0.37% |
Timeline
The attack was preceded by an extortion email received two days earlier. Request rates on the targeted routes exceeded their hourly baseline by a factor of 672 within 16 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
- Add a dedicated rate limit for the targeted route.
- Enable log streaming to your SIEM for faster correlation.
- Enable authenticated origin pulls.
Our auditors asked for exactly this kind of incident evidence under DORA.
Carpet bombing is nasty. Good to see a clear explanation of it.
Would love a follow-up on how you handle HTTP/3 fingerprinting.
Do you publish the edge IP ranges in a machine-readable format?
Nice to read a vendor blog that admits what went wrong.
Could you share the dataset behind the percentages?
Would love a follow-up on how you handle HTTP/3 fingerprinting.