On Monday 23 October 2023 at 20:22 UTC, a SYN flood targeted a municipal services customer in Central Europe. The attack peaked at 63.9 Gbps and lasted 27 minutes. Traffic originated from 3409 autonomous systems in 10 countries, predominantly a headless-browser farm.
| Vector | SYN flood |
| Peak | 63.9 Gbps |
| Duration | 27 min |
| Time to mitigation | 0.370 s |
| Attack traffic reaching origin | 0.084% |
| Legitimate traffic challenged | 0.15% |
Timeline
The attack was preceded by a publicly announced sales event. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 39 points of presence.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Keep origin IPs out of public DNS history.
- Add a dedicated rate limit for the targeted route.
- Lower challenge thresholds on authentication endpoints during high-risk events.