On Thursday 20 March 2025 at 17:34 UTC, a WebSocket connection flood targeted a retail banking customer in the Nordics. The attack peaked at 157.0 million requests per second and lasted 110 minutes. Traffic originated from 2181 autonomous systems in 45 countries, predominantly compromised cloud VMs.
| Vector | WebSocket connection flood |
| Peak | 157.0 million requests per second |
| Duration | 110 min |
| Time to mitigation | 0.078 s |
| Attack traffic reaching origin | 0.042% |
| Legitimate traffic challenged | 0.39% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 833 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
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.
- Add a dedicated rate limit for the targeted route.