On Friday 12 September 2025 at 03:01 UTC, a HTTP/2 rapid reset targeted a healthcare portal customer in the Nordics. The attack peaked at 790.3 million requests per second and lasted 185 minutes. Traffic originated from 1075 autonomous systems in 42 countries, predominantly compromised cloud VMs.
| Vector | HTTP/2 rapid reset |
| Peak | 790.3 million requests per second |
| Duration | 185 min |
| Time to mitigation | 0.826 s |
| Attack traffic reaching origin | 0.024% |
| Legitimate traffic challenged | 0.66% |
Timeline
The attack was preceded by a competitor’s product launch. Request rates on the targeted routes exceeded their hourly baseline by a factor of 478 within 29 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
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Keep origin IPs out of public DNS history.
- Review allow-listed partner ranges quarterly.
- Enable log streaming to your SIEM for faster correlation.
Is the risk score exposed in the logs so we can build our own dashboards on it?
This matches what we see in iGaming around big matches.
Thanks — sharing this with our on-call team.