On Thursday 28 May 2026 at 07:45 UTC, a cache-busting query flood targeted a healthcare portal customer in the UK. The attack peaked at 349.6 million requests per second and lasted 39 minutes. Traffic originated from 285 autonomous systems in 20 countries, predominantly a headless-browser farm.
| Vector | cache-busting query flood |
| Peak | 349.6 million requests per second |
| Duration | 39 min |
| Time to mitigation | 0.185 s |
| Attack traffic reaching origin | 0.049% |
| Legitimate traffic challenged | 0.37% |
Timeline
The attack was preceded by a hacktivist channel announcing the target. Request rates on the targeted routes exceeded their hourly baseline by a factor of 573 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
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.
- Enable log streaming to your SIEM for faster correlation.