On Friday 20 August 2021 at 00:11 UTC, a HTTP/2 rapid reset targeted a video streaming customer in Central Europe. The attack peaked at 958.6 million requests per second and lasted 63 minutes. Traffic originated from 3782 autonomous systems in 96 countries, predominantly hijacked home routers.
| Vector | HTTP/2 rapid reset |
| Peak | 958.6 million requests per second |
| Duration | 63 min |
| Time to mitigation | 0.204 s |
| Attack traffic reaching origin | 0.042% |
| Legitimate traffic challenged | 0.80% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 665 within 31 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 104 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.