On Sunday 19 January 2025 at 05:15 UTC, a SYN flood targeted a developer platform customer in Western Europe. The attack peaked at 211.2 Gbps and lasted 122 minutes. Traffic originated from 962 autonomous systems in 25 countries, predominantly a headless-browser farm.
| Vector | SYN flood |
| Peak | 211.2 Gbps |
| Duration | 122 min |
| Time to mitigation | 0.039 s |
| Attack traffic reaching origin | 0.072% |
| Legitimate traffic challenged | 0.12% |
Timeline
The attack was preceded by a competitor’s product launch. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 26 points of presence.
What the customer saw
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Add a dedicated rate limit for the targeted route.
- Keep origin IPs out of public DNS history.
Is the risk score exposed in the logs so we can build our own dashboards on it?
The point about origin IPs leaking through certificate transparency logs is underrated.