On Tuesday 25 May 2021 at 13:54 UTC, a HTTP/2 rapid reset targeted a developer platform customer in North America. The attack peaked at 199.1 million requests per second and lasted 98 minutes. Traffic originated from 3067 autonomous systems in 46 countries, predominantly residential proxy networks.
| Vector | HTTP/2 rapid reset |
| Peak | 199.1 million requests per second |
| Duration | 98 min |
| Time to mitigation | 0.195 s |
| Attack traffic reaching origin | 0.090% |
| Legitimate traffic challenged | 0.21% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 642 within 34 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
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Enable authenticated origin pulls.
- Enable log streaming to your SIEM for faster correlation.
- Lower challenge thresholds on authentication endpoints during high-risk events.