On Wednesday 29 April 2026 at 03:14 UTC, a WebSocket connection flood targeted a healthcare portal customer in Central Europe. The attack peaked at 750.9 million requests per second and lasted 130 minutes. Traffic originated from 1191 autonomous systems in 86 countries, predominantly compromised cloud VMs.
| Vector | WebSocket connection flood |
| Peak | 750.9 million requests per second |
| Duration | 130 min |
| Time to mitigation | 0.481 s |
| Attack traffic reaching origin | 0.000% |
| Legitimate traffic challenged | 0.35% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 662 within 6 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 99 ms during the first minute, then normal service.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.
- Lower challenge thresholds on authentication endpoints during high-risk events.
The point about origin IPs leaking through certificate transparency logs is underrated.
Great write-up. We saw almost the same pattern on our login endpoint last month.
Good question. We will cover that in a follow-up post.
This matches what we see in iGaming around big matches.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.