On Saturday 8 April 2023 at 02:32 UTC, a HTTP/2 rapid reset targeted a developer platform customer in Western Europe. The attack peaked at 196.8 million requests per second and lasted 20 minutes. Traffic originated from 3618 autonomous systems in 45 countries, predominantly misconfigured open reflectors.
| Vector | HTTP/2 rapid reset |
| Peak | 196.8 million requests per second |
| Duration | 20 min |
| Time to mitigation | 0.222 s |
| Attack traffic reaching origin | 0.079% |
| Legitimate traffic challenged | 0.29% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 695 within 5 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
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Thanks! Yes — the risk score and its components are included in every log record.
Our auditors asked for exactly this kind of incident evidence under DORA.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
Nice to read a vendor blog that admits what went wrong.
Thanks — sharing this with our on-call team.