On Wednesday 15 January 2025 at 07:14 UTC, a HTTP/2 rapid reset targeted a tax authority portal customer in Central Europe. The attack peaked at 949.3 million requests per second and lasted 137 minutes. Traffic originated from 1901 autonomous systems in 8 countries, predominantly hijacked home routers.
| Vector | HTTP/2 rapid reset |
| Peak | 949.3 million requests per second |
| Duration | 137 min |
| Time to mitigation | 0.422 s |
| Attack traffic reaching origin | 0.049% |
| Legitimate traffic challenged | 0.13% |
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 87 within 20 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 53 ms during the first minute, then normal service.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Review allow-listed partner ranges quarterly.